SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY
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Section A: Basic Microbiology 1 SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY “Science contributes to our culture in many ways, as a creative intellectual activity in its own right, as a light which has served to illuminate man’s place in the uni-verse, and as the source of understanding of man’s own nature” —John F. Kennedy (1917–63) The President of America The bacterium Escherichia coli INTRODUCTION AND SCOPE MICROBIOLOGY is a specialized area of biology (Gr. bios-life+ logos-to study) that concerns with the study of microbes ordinarily too small to be seen without magnification. Microorganisms are microscopic (Gr. mikros-small+ scopein-to see) and independently living cells that, like humans, live in communities. Microorganisms include a large and diverse group of microscopic organisms that exist as single cell or cell clusters (e.g., bacteria, archaea, fungi, algae, protozoa and helminths) and the viruses, which are microscopic but not cellular. While bacteria and archaea are classed as prokaryotes (Gr. pro-before+ karyon-nucleus) the fungi, algae, protozoa and helminths are eukaryotes (Gr. eu-true or good+ karyon-nucleus). Microorganisms are present everywhere on earth, which includes humans, animals, plants and other living creatures, soil,water and atmosphere. Microorganisms are relevant to all of our lives in a multitude of ways. Sometimes, the influence of microorganisms on human life is beneficial, whereas at other times, it is detrimental. For example, microorganisms are required for the production of bread, cheese, yogurt, alcohol, wine, beer, antibiotics (e.g., penicillin, streptomycin, chloramphenicol), vaccines, vitamins, enzymes and many more important products as shown in the Tables 1.1, 1.2, and 1.3. Many products of microbes contribute to public health as aids to nutrition, other products are used to interrupt the spread of disease, still others hold promise for improving the quality of life in the year’s ahead. 1 2 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY Table 1.1: Major antibiotics and their microbial sources Antibiotic Microbial source Bacillus licheniformis Cephalosporium acremonium Streptomyces venezuelae Streptomyces griseus Streptomyces orchidaceus Streptomyces erythraeus Penicillium griseofulvum Streptomyces kanamyceticus Streptomyces lincolnensis Streptomyces fradiae Streptomyces noursei Penicillium chrysogenum Bacillus polymyxa Streptomyces griseus Actinoplanes teichomyceticus Streptomyces rimosus Streptomyces orientalis Bacitracin Cephalosporin Chloramphenicol Cycloheximide Cycloserine Erythromycin Griseofulvin Kanamycin Lincomycin Neomycin Nystatin Penicillin Polymyxin B Streptomycin Teicoplanin Tetracycline Vancomycin Table 1.2: Major industrial enzymes from bacteria, molds and yeasts and their applications Enzyme Microorganism Application Bacterial Enzymes Amylase (α and β ) Bacillus Glucose isomerase Penicillin amidase Protease Bacillus, Streptomyces Bacillus Bacillus Mold Enzymes α-Amylase Glucoamylase Aspergillus Aspergillus, Rhizopus Rennet (aspartic proteinases) Pectinase Protease (aspartic proteinases) Cellulase Mucor miehei Aspergillus, Sclerotinia Aspergillus Aspergillus, Trichoderma Starch coatings (paper), desizing (textiles), removal of stains, detergents (drycleaning) Fructose syrup Pharmaceutical Detergent, spot removing, desizing, wound cleaning Baking (Bread) Syrup and glucose manufacture, digestive aid (pharmaceutical) Cheese Drinks Baking Liquid, coffee concentrates, digestive aid, degradation of wood or wood byproducts SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY Enzyme Microorganism α-Galactosidase (commercial name Beano) 3 Application Aspergillus niger Pharmaceutical (helps in digestion of sugar in humans) Confectionary Lactase (β-galactosidase) Saccharomyces Kluyveromyces Raffinase (α-galactosidase) Saccharomyces Food Yeast Enzymes Invertase Dairy Table 1.3: Fermented foods from microorganisms Fermented Food Substrate Idli Rice and Urad bean Ang-kak Gari Rice Cassava Kaffir beer Yoghurt Sorghum caffrorum or Eleusine coracana Milk Milk Cheese Milk Kefir Microorganism Leuconostoc mesenteroides, Streptococcus faecalis Monascus purpureus Corynebacterium manihot, Geotrichum candidum Lactobacillus delbrueckii Saccharomyces cerevisiae Lactobacillus and Yeast Streptococcus thermophilus, Lactobacillus bulgaricus Penicillium roqueforti P. camemberti Country/ region India China West Africa South Africa Russia Worldwide Worldwide Microbes are also an important and essential component of an ecosystem. Molds and bacteria play key roles in the cycling of important nutrients in plant nutrition particularly those of carbon, nitrogen and sulphur. Bacteria referred to as nitrogen fixers live in the soil where they convert vast quantities of nitrogen in air into a form that plants can use. Microorganisms also play major roles in energy production. Natural gas (methane) is a product of bacterial activity, arising from the metabolism of methanogenic bacteria. Microoragnisms are also being used to clean up pollution caused by human activities, a process called bioremediation (the introduction of microbes to restore stability to disturbed or polluted environments). Bacteria and fungi have been used to consume spilled oil, solvents, pesticides and other environmentally toxic substances. Microorganisms have also harmed humans and disrupted societies over the millennia. Microbial diseases undoubtedly played a major role in historical events, it was in the year 1347 when plague or ‘black death’ struck Europe and within 4 years killed 25 million people, that is, one third of the population. Some of the common human diseases caused by bacteria, fungi (molds and yeasts), protozoa, helminths are shown in the Tables 1.4–1.7. 4 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY Table 1.4: Human diseases caused by bacteria Type Species Disease Spirochetes Treponema pallidum Borrelia recurrentis Borrelia burgdorferi Leptospira interrogans Syphilis Relapsing fever Lyme disease Leptospirosis Helical, vibrioid, Gramnegative bacteria Campylobacter jejuni Helicobacter pylori (=Campylobacter pylori) Food borne campylobacter enteritis Peptic ulcer and chronic gastritis Gram-negative aerobic rods and cocci Legionella pneumophila Neisseria gonorrhoeae Neisseria meningitidis Brucella melitensis Bordetella pertussis Francisella tularensis Legionnaires’ disease Gonorrhoea Meningococcal meningitis Brucellosis Whooping cough Tularemia (Rabbit fever) Facultatively aerobic, Gram-negative rods Escherichia coli Salmonella typhi Shigella dysenteriae Klebsiella pneumoniae Proteus sp. Yersinia pestis Vibrio cholerae Haemophilus influenzae Gardnerella vaginalis Oppurtunistic infections Typhoid fever Bacillary dysentry (Shigellosis) Pneumonia, Meningitis Urinary tract infections Bubonic plague Cholera Meningitis, Ear infections Vaginitis Rickettsias and Chlamydias Rickettsia rickettsiae Rickettsia prowazekii Rickettsia typhi Coxiella burnetii Chlamydia trachomatis Chlamydia psittaci Chlamydia pneumoniae Rocky mountain spotted fever Epidemic typhus Murine typhus Q-Fever Trachoma Ormithosis (Psittacosis) Pneumonia Mycoplasmas Mycoplasma pneumoniae Primary atypical pneumonia Gram-positive cocci Staphylococcus aureus Boils, wound infections, Toxic shock syndrome, Food poisoning, Impetigo Pneumococcal pneumonia Strep throat, Glomerulonephritis, Rheumatic fever, Impetigo Dental caries Streptococcus pneumoniae Streptococcus pyogenes Streptococcus mutans (Contd.) SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY Type Species Disease Bacillus anthracis Clostridium tetani Anthrax Clostridium perfringens Gas gangrene Clostridium botulinum Botulism Clostridium difficile Pseudomembranous colitis Regular, non-sporing Lactobacillus sp. Normal human flora Gram-positive rods Listeria monocytogenes Listeriosis Irregular, non-sporing, Corynebacterium diphtheriae Diphtheria Gram-positive rods Propionibacterium acne Acne Spore forming Grampositive rods and cocci Tetanus Mycobacteria (Acid- fast Mycobacterium tuberculosis Mycobacterium leprae organisms) 5 Tuberculosis Leprosy Table 1.5: Human diseases caused by fungi Disease Pathogen (A) Superficial mycoses Black piedra White piedra Dandruff or Tinea versicolor Piedraia hortae Trichosporon beigelii Malassezia furfur (Pityrosporum ovale) (B) Dermatomycoses ( cutaneous mycoses) Tinea capitis (Ringworm) Microsporum audouinii Tinea pedis (Athlete’s foot) Trichophyton spp. Tinea cruris (Jock itch) Epidermophyton floccosum Tinea unguium (Ringworm of nails) Trichophyton rubrum (C) Subcutaneous mycoses Chromoblastomycosis Maduromycosis Sporotrichosis Fonsecaea pedrosoi (Phialophora verrucosa) Madurella mycetomatis Sporothrix schenckii (D) Systemic mycoses (deep mycoses) Blastomycosis Coccidioidomycosis (valley fever) Cryptococcosis Histoplasmosis Blastomyces dermatitidis (Ajellomyces dermatitidis) Coccidioides immitis Cryptococcus neoformans (Filobasidiella neoformans) Histoplasma capsulatum (Contd.) 6 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY Disease Pathogen (E) Opportunistic mycoses Aspergillosis Candidiasis (oral, napkin (diaper) Aspergillus fumigatus Candida albicans candidiasis, Candidal vaginitis) Pneumocystis pneumonia (PCP) Zygomycosis (F) Food poisoning Ergotism (ergot poisoning) Pneumocystis jiroveci (P.carinii) Mucor and Rhizopus spp. Claviceps purpurea Table 1.6: Human diseases caused by protozoans Phylum Pathogen Apicomplexa Rhizopoda Mastigophora (Flagellata) Ciliophora (Ciliata) Disease Babesia microti Plasmodium falciparum, P. ovale, P. vivax, P. malariae Toxoplasma gondii Cryptosporidium parvum Babesiosis Acanthamoeba sp. Entamoeba histolytica Naegleria fowleri Amoebic keratitis Malaria Toxoplasmosis Cryptosporidiosis Amoebic dysentery Microencephalitis Giardia lamblia (G. Intestinalis) Trichomonas vaginalis Trypanosoma brucei Trypanosoma cruzi Giardiasis Balantidium coli Balantidial dysentery Protozoal vaginitis African sleeping sickness Chaga’s disease Table 1.7: Human diseases caused by helminths Phylum Platyhelminthes Pathogen Paragonimus westermanni (Lung fluke) Schistosoma sp. (Blood flukes) Clonorchis sinensis (Chinese liver fluke) Disease Paragonimiasis Schistosomiasis Clonorchiasis (Contd.) SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY Phylum Pathogen Taenia saginata (Beef tapeworm) Taenia solium (Pork tapeworm) Hymenolepsis nana (Dwarf tapeworm) Diphyllobothrium latum (Fish tapeworm) Echinococcus granulosus (Dog tapeworm) Fasciola hepatica (Sheep liver fluke) Nematoda (Roundworms) Strongyloides stercoralis (Threadworm) Ascaris lumbricoides (roundworm) Necator americanus (hookworm) Ancylostoma duodenale (hookworm) Enterobius vermicularis (Pinworm) Trichuris trichiura (Whipworm) Trichinella spiralis (Trichinaworm) Wuchereria bancrofti 7 Disease Taeniasis Taeniasis Hymenolepasis Diphyllobothriasis Echinococcosis Fascioliasis Strongyloidiasis Ascariasis New world hookworm disease Old world hookworm disease Pinworm feotalism Trichuriasis Trichinosis Elephantiasis or bancroftian filariasis Dirofilaria immitis (Heartworm) Filariasis HISTORICAL DEVELOPMENTS IN MICROBIOLOGY The beginnings The study of microorganisms, or microbiology began when the first microscopes were developed in 1665 by the English scientist, Robert Hooke who viewed many small objects and structures using a simple lens that magnified approximately 30 times. His specimens included the eye of a fly, a bee stinger, and the shell of a protozoan. Hooke also examined thin slices of cork, which was the bark of a particular type of oak tree. He found that cork was made of tiny boxes that Hooke referred to as ‘cells’. He published his work in a book Micrographie which contained a miscellany of his thoughts on chemistry as well as a description of the microscope and its uses. Hooke in 1665 described the fruiting structures of molds. Thus, Robert Hooke was the first person to describe microorganisms. 8 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY MICROFOCUS 1.1 Antony van Leeuwenhoek (pronounced Layu-wen- hoek) was born on October 24, 1632 in Delft, Holland (now Netherlands). In 1674, he made first observation of microoraganisms and was the first person to observe and accurately describe and measure bacteria and protozoa, termed by him, as “animalcules” which he thought were tiny animals. In 1677, he became the first person to describe spermatozoa and was one of the earliest to describe red blood corpuscles. In 1680, he was elected a fellow of the Royal Society of London, and with Isaac Newton and Robert Boyle, he became one of the first famous men of his time. He died on August 30, 1723 at the age of 90. Because of his extraordinary contribution to microbiology, he is considered as the father of bacteriology and protozoology. Antony van Leeuwenhoek (1632-1723) Unicellular life was first described just a few years after Hooke recorded his observations of the microscopic world. Antony van Leeuwenhoek (Microfocus 1.1) was a Dutch merchant who polished grains of sand into lenses which were able to magnify 300 times and added a simple focus mechanism. With his microscope, van Leeuwenhoek viewed rain and pond water, infusions made from peppercorns, and scrapings from his teeth in the year 1674 and termed the tiny microorganisms as ‘animalcules’. In 1676, van Leeuwenhoek sent his drawings to the Royal Society of London. This has special significance to microbiology because it contained his first detailed description of the microorganism. The transition period Biology of the 1700s was a body of knowledge without a focus. It consisted of observations of plant and animal life and the attempts by scientists to place the organisms in logical order. The dominant figure of the era was Carolus Linnaeus (1707–1778), a Swedish botanist who brought all the plant and animal forms together under one Binomial nomenclature (naming of an organism by two names—the genus and species) system of classification scheme. His book, Systema naturae, was first published in 1735. Discovery of the microscopic world raised some interesting queries and eventually led scientists to question some of the long-held beliefs. At that time in history, the scientific community used a theory known as ‘spontaneous generation’ (the doctrine that holds that lifeless objects give rise to living organisms) to explain the apparently magical origins of life. The theory proposed that simple life forms arose spontaneously from non-living materials and had its basis in the findings of Aristotle in the fourth century BC. Although most people accepted spontaneous generation, the theory did have some strong opponents. Among the first to dispute the theory of spontaneous generation was the Italian scientist, Francesco Redi (1626–1697). He reasoned that flies had reproductive organs while observing van Leeuwenhoek’s drawings. He suggested that flies land on pieces of exposed meat and lay their eggs, which then hatch to maggots. This would explain the ‘spontaneous’ appearance of maggots. In the 1670s, Redi performed a series of tests in which he covered jars of meat with fine lace, thereby preventing the entry of flies. The meat would not produce maggots as it was protected and Redi temporarily put to rest the notion of spontaneous generation. SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY 9 Although Redi’s work became widely known, the doctrine of spontaneous generation was too firmly entrenched to be abandoned. In 1748, British clergyman, John Needham (1713–81) put forth the notion that in flasks of mutton gravy, microorganisms arise by spontaneous generation. He even boiled several flasks of gravy and sealed the flasks with corks as Redi had sealed his jars. Still, the microorganisms appeared. Italian scientist Abbe Lazzaro Spallanzani (1729–99) criticized Needham’s work. In 1767, Spallanzani boiled meat and vegetable broths for long period of time and then sealed the necks by melting the glass. As control experiments, he left some flasks open to the air, stoppered some loosely with corks, and boiled some briefly, as Needham had done. After two days, he found the control flasks swarming with organisms, but the sealed flasks had no organisms. Needham countered that Spallanzani had destroyed the ”vital force” of life with excessive amounts of heat. While the spontaneous generation was being debated, some of the scientists were concerned about the transmission of the disease. In 1546, Italian scientist Girolamo Fracastoro held the concept that “contagion is an infection that passes from one thing to another”. He recognized three forms of passage, namely contact, lifeless objects, and air (Table 1.8). This notion received little credibility that microorganisms were the substance of contagion. The German Athanasius Kircher was paid little attention when he reported “microscopic worms” in the 1600s in the blood of plague victims. Christian Fabricius was also neglected when he suggested in 1700s that fungi might be the cause of rust and smut diseases in plants. Edward Jenner (Microfocus 1.2) was accorded honours in 1798 when he discovered immunization for smallpox, despite the fact that he could not explain the cause of the disease. In 1847, Hungarian physician, Ignaz Semmelweis reported that blood poisoning agent was transmitted to maternity patients by physicians fresh from performing autopsies in the mortuary. Semmelweis showed that hand washing in chlorine water could stop the spread of disease. His call for disinfection practices were however largely unheeded because it implied that physicians were at fault. MICROFOCUS 1.2 Edward Jenner, born in 1749, was an English physician from Berkeley, Gloucestershire, England. His great gift to mankind was his vaccine for smallpox (characterized by production of skin lesions called pox (pocks), caused by Variola, belonging to the category of pox viruses). Jenner’s discovery, that a less pathogenic agent could confer protection against a more pathogenic one, is especially remarkable in view of the fact that microscopy was still in its infancy and the nature of the virus was not known. The modern era of vaccines and vaccination, thus began in 1798 with Edward Jenner’s use of cowpox as a vaccine against smallpox. Edward Jenner (1749–1823) John Snow, a British physician, traced the source of cholera to the municipal water supply of London during an 1854 outbreak. He reasoned that by avoiding the contaminated water source, people could avoid the disease. Snow’s recommendations were adopted and the spread of disease was halted. Both Semmelweis and Snow drew attention to the fact that a poison or unseen object in the environment was responsible for the disease, but the proof was still lacking. Joseph Lister (Microfocus 1.3) in 1867, developed a system of antiseptic surgery designed to prevent microorganisms from entering wounds. 10 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY MICROFOCUS 1.3 Joseph Lister was born in 1827. He developed a system of antiseptic surgery designed to prevent microorganisms from entering wounds in 1867. In 1878, Lister studied the lactic acid fermentation of milk and demonstrated the specific cause of milk souring. He also developed a method for isolating a pure culture of a bacterium, named as Bacterium lactis. Because of his notable contribution-first introduction of principles of sterile surgery in medical practice, which was so far reaching in its effects—Lister will always be known as the Father of antiseptic surgery. He died at the age of 85 in the year 1912. Joseph Lister (1827–1912) Table 1.8: Some early observations in microbiology before the dawn of golden era Time period Investigator Observations Fourth Century BC. Aristotle Living things do not need parents, spontaneous generation apparently occurs. Mid 1500s Fracastoro “Contagion” passes among individuals, objects and air. Mid 1600s Kircher “Microscopic worms” are present in blood of plague victims. Mid 1600s Francisco Redi Fly larvae arise by spontaneous generation. Late 1600s Van Leeuwenhoek Microscopic organisms are present in numerous environments. Early 1700s Christian Fabricius Fungi cause rust and smut diseases in plants. Early 1700s Joblot Existence of various forms of protozoa. Mid 1700s John Needham Microorganisms in broth arise by spontaneous generation. Mid 1700s Lazzaro Spallanzani Heat destroys microorganisms in broth. Late 1700s Edward Jenner Recoverers from cowpox do not contract smallpox. Mid 1800s Ignaz Semmelweis Chlorine disinfection prevents disease spread. Mid 1800s John Snow Water is involved in disease transmission. The classical golden age of microbiology (1854–1914) The science of microbiology blossomed during a period of about 60 years referred to as the Golden Era of Microbiology. The period began in 1857 with the work of Louis Pasteur and continued into the twentieth century until the advent of World War I. During this period, numerous branches of microbiology were laid for the maturing process that has led to modern microbiology. Louis Pasteur (Microfocus 1.4) was the first to report the role of microorganisms in fermentation in 1848, he achieved distinction in organic chemistry for his discovery that tartaric acid, a fourcarbon organic compound, forms two different types of crystals. Pasteur successfully separated the crystals while looking through the microscope. In 1854, at the age of 32, he was appointed Professor of Chemistry at the University of Lille in northern France. Pasteur in 1857 unravelled the mystery of sour wines. In a classic series of experiments, Pasteur clarified the role of yeasts in fermentation of fruits and grains resulting in the production of alcohol. SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY 11 He also found that bacteria were responsible for spoilage of wine. He firmly disproved the spontaneous generation doctrine by his Swan-Neck Flask experiment (Fig. 1.1). He proposed germ theory of disease and discovered the existence of life in the absence of free oxygen (anaerobic growth). He showed that mild heating could be used to kill microorganisms in broth (pasteurization). Pasteur suggested methods to control pebrine disease in silkworm, isolated the causative agent of cholera (Vibrio cholerae) and rabies (Lyssa) virus and also developed anti rabies and anthrax (Bacillus anthracis) vaccines. Although Pasteur failed to relate a specific organism to a specific disease, his work stimulated others to investigate the nature of microorganisms and to ponder their association with disease. German botanist, Ferdinand Cohn (1828–98), discovered that bacteria multiply by dividing into two cells. He also observed that certain bacteria form an extremely resistant structure called endospore in the cell. Fig. 1.1: Pasteur’s experiment with the swan-necked flasks to disprove spontaneous generation. (a) Life appeared in broth in flasks exposed to air. (b) No life appeared in sealed flasks. (c) No life appeared in flasks where the neck was continuously heated. (d) No life appeared in flasks when the microorganisms were trapped in the bend of the side arm. 12 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY MICROFOCUS 1.4 Louis Pasteur- Notable Contributions 1857 1860 1861 1861 – – – – Lactic acid fermentation is due to a microorganism Yeasts are involved in alcoholic fermentation Disproved the theory of spontaneous generation Introduction of the terms aerobic and anaerobic for yeasts. Production of more alcohol in the absence of oxygen during sugar fermentation- The Pasteur Effect 1862 – Proposed germ theory of disease 1867 – Pasteur devised the process of destroying bacteria known as pasteurization. 1881 – Development of anthrax vaccine. Resolved Pebrine problem of silkworms. 1885 – Development of a special vaccine for rabies (the Pasteur Louis Pasteur treatment) (1822–1895) Louis Pasteur, a French microbiologist, was born on December 27, 1822 in Dole, France. He studied at the French school, the Ecole Normale Superieure. In 1848, he achieved distinction in organic chemistry for his discovery that tartaric acid, a four carbon organic compound forms two different types of crystals. Using a microscope, Pasteur successfully separated the crystals and developed a skill that would aid his later studies of microorganisms. In 1854, at the young age of 32, he was appointed Professor of Chemistry at the University of Lille in northern France. He died in 1895, at the age of 73. Cohn described the entire life cycle of Bacillus (vegetative cell → endospore → vegetative cell). He is credited with the use of cotton plugs for closing flasks and tubes to prevent the contamination of sterile culture media. In 1866, Cohn studied the filamentous sulphur-oxidizing bacterium Beggiatoa mirabilis and was the first to identify the small granules present in the cell that are of sulphur, produced from the oxidation of H2S. The definite proof of the germ theory of disease was offered by Robert Koch (Microfocus 1.5) from East Russia, now part of Germany. Koch’s primary interest was anthrax, a deadly blood disease in cattle and sheep. In 1875, he injected mice with the blood of diseased sheep and cattle. He then performed meticulous autopsies and noted that the same symptoms appeared regularly. He isolated a few rod shaped bacilli from a mouse’s blood by placing the bacilli in the sterile aqueous humor from an ox’s eye. The symptoms of anthrax appeared within hours. Koch autopsied the animals and found their blood swarming with bacilli. He reisolated the bacilli in sterile aqueous humor. Koch’s procedures came to be known as Koch’s postulates (Fig. 1.2). The four postulates are: • The suspected microorganism must always be found in diseased but never in healthy individuals. • The microorganism must be isolated in pure culture (one free of all other types of microbes) on a nutrient medium. • The same disease must result when the isolated microorganism is inoculated into a healthy host. • The same organism must be reisolated from the experimentally infected host. SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY 13 Fig. 1.2: The diagrammatic representation of the Koch’s criteria for proving that a specific microorganism causes a specific disease, i.e., the Koch’s postulates. MICROFOCUS 1.5 Notable contributions of Robert Koch 1876 – Koch demonstrated that anthrax is caused by Bacillus anthracis. 1877 – Methods for staining bacteria, photographing and preparing permanent visual records on slides. 1881 – Koch developed solid culture media and the methods for studying bacteria in pure cultures. 1882 – Isolated the bacterium—Mycobacterium tuberculosis—that causes tuberculosis. 1882 – Use of agar as a support medium for solid culture in Koch’s lab by Hesse. 1883 – Isolation of Vibrio cholerae, the cause of cholera. 1883 – Verification of the germ theory of disease by relating a specific organism to the specific disease. 1884 – Koch put forth his postulates—known as Koch’s postulates. Robert Koch (1843–1910) Robert Koch was born in Hanover, Germany in 1843. For his contributions on tuberculosis, Robert Koch was awarded the 1905 Nobel Prize for Physiology or Medicine. He died in the year 1910 at the age of 67. 14 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY Koch chanced to observe in 1880 that a slice of potato contained small masses of bacteria, which he termed colonies. Colonies contained millions of just one kind of bacteria. Koch concluded that bacteria could grow and multiply on solid surfaces, and he added gelatin to his broth to prepare a solid culture medium. He then inoculated bacteria to the surface and set the medium aside to incubate. When colonies of the same bacterium grew together, a pure culture (an accumulation of one type of microorganism formed by the growth of colonies of the organism) formed. Koch could now inoculate laboratory animals with a pure culture of bacteria and be certain that only one species of bacterium was involved. His work also proved that bacteria, not toxins in the broth were the cause of the disease. Gelatin was replaced with agar as a solidifying agent in the culture media as suggested by Fannie Eilshemius Hesse, wife of Walter Hesse, an assistant in the Koch’s lab. Petri dish was also invented about this time by Julius Petri, one of Koch’s assistants. In 1881, Koch demonstrated his pure culture techniques in the International Medical Congress. Koch’s proof of the germ theory was presented in 1876. Within two years, Pasteur had verified the proof and gone a step further. He reported that bacteria were temperature-sensitive because chickens did not acquire anthrax at their normal body temperature of 420C but did so when the animals were cooled down to 370C. He also recovered anthrax spores from the soil and pointed out that cattle were probably infected during grazing. This explained the periodic recurrence of the disease. One of Pasteur’s more remarkable discoveries was made in 1880 when a group of inoculated chickens failed to develop chicken cholera. He had been working on ways to enfeeble bacteria using heat, different growth media, passages among animals, and virtually anything he thought might weaken them. Finally, he had developed two cultures whose ability to cause disease was reduced. The trick was to suspend the bacteria in a mildly acidic medium and allow the culture to remain undisturbed for a long period of time.When it was inoculated to chickens and later followed by a dose of lethal cholera bacilli, the animals did not become sick. This principle is the basis for the use of many vaccines for immunity. Pasteur applied the principle to anthrax in 1881 and found he could protect sheep against the disease. Koch, isolated the tubercle bacillus, the cause of tuberculosis. In 1884, Koch’s associate George Gafky, cultivated the typhoid bacillus, and that same year another coworker, Friederich Loeffler, isolated the diphtheria bacillus. In later years, Koch’s coworker, Emil von Behring, successfully treated diphtheria by injecting antitoxin, a blood product (preparation of antibodies) obtained from animals given injections of the toxin. For his work, von Behring was awarded the first Nobel Prize in Physiology or Medicine.In 1885, Pasteur reached the zenith of his carrier when he successfully immunized young Joseph Meister against the dreaded disease rabies. Although he never saw the agent of rabies, Pasteur was able to cultivate it in the brains of animals and inject the boy with bits of the tissue. The experiment was a triumph for Pasteur because it fulfilled his dream of applying the principles of science to practical problems. A comparison of Pasteur and Koch’s achievements is given in the Table 1.9. Other pioneers of microbiology Shibasaburo Kitasato of Japan studied with Koch and successfully cultivated the tetanus bacillus, an organism that grows only in the absence of oxygen. One of the Pasteur’s associates was Elie Metchnikoff (Microfocus 1.6), who in 1884, published an account of phagocytosis, a defensive process in which the body’s white blood cells engulf and destroy microorganisms. SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY 15 Table 1.9: A comparison of contributions of Louis Pasteur and Robert Koch Characteristic Louis Pasteur Robert Koch Country of origin Preparatory education France Chemistry Germany (Prussia) Medicine Initial investigations Milk souring, beer, wine fermentations Cause of anthrax Accomplishments • Proposed germ theory of disease • Disproved theory of spontaneous generation • Developed immunization techniques • Resolved pebrine problem of silkworms • Developed rabies vaccine Associates Roux, Yersin, Metchnikoff Nobel Prize No • Proved germ theory of disease • Developed cultivation methods for bacteria • Isolated bacterium that causes tuberculosis • Developed staining methods for bacteria • Investigated cholera, malaria, sleeping sickness Gaffky, Loeffler, von Behring, Richard Pfeiffer 1905 Nobel Prize in Physiology or Medicine MICROFOCUS 1.6 Elie Metchnikoff, one of the associates of Louis Pasteur, was a Russian zoologist who lived in Paris and did his work at the Institute Pasteur, France. He was born in Kharkor priovince of Ukraine (USSR) in 1845. By the 1860s he had completed his formal studies in Embryology from various Universities of Kharkor, Russia, Germany and Italy. Metchnikoff coined the term “phagocytosis” which literally means” the eating of cells”. In 1884, he published account of phagocytosis, a defensive process in which the body’s white blood cells (WBCs) engulf and destroy microorganisms. Thus, he formulated the basic theory on which the science of immunology is founded: that the body is protected from infection by leukocytes that engulf bacteria and other invading organism (cellular immunity). He became an administrator to the Institute Pasteur in 1888 and eventually became its director. He was awarded the Nobel Elie Metchnikoff Prize in 1908. Metchnikoff’s notable contribution was on the Bacillus bulgaricus (1845–1916) therapy and his underlying concept of health. Metchnikoff belived that streptococci and lactobacilli in yogurt assume residence in the intestine and replace organisms that contribute to aging. Despite eating large quantities of yogurt, Metchnikoff died an early death, in 1916, at age seventy-one. A Pasteur Institute scientist, Charles Nicolle, proved that typhus fever was transmitted by lice. Albert Calmette, also of the Institute, developed a harmless strain of the Tubercle bacillus used for immunization. Jules Bordet, a Belgian bacteriologist isolated the bacillus of pertussis (whooping cough) and developed the complement fixation test, a procedure once widely used in the diagnosis of disease. 16 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY Ronald Ross, an English physician working in the Far East in 1898 proved that mosquitoes were the vital link in malaria transmission. The discovery earned him the 1902 Nobel Prize. Another Englishman, David Bruce, isolated the cause of undulant fever. Bruce also showed that tsetse flies transmit sleeping sickness. A third British subject, Almroth Wright, described opsonins, the chemical substances that promote phagocytosis in the body. In 1897, the Tokyo physician Masaki Ogata reported that rat fleas transmit bubonic plague. This discovery solved a centuries old mystery of how plague spread. A year later, Kiyoshi Shiga isolated the bacterium that causes bacterial dysentery, an important intestinal disease. The organism was later named Shigella. The American microbiologists, Daniel E. Salmon and Theobald Smith, were among the first to use heat killed bacteria for immunizations. Salmon later studied swine plague and lent his name to Salmonella, the cause of typhoid fever. Smith showed that Texas fever, a disease of cattle, was transmitted by ticks. The University of Chicago pathologist Howard Taylor Rickkets located the agent of Rocky Mountain spotted fever in the human bloodstream and demonstrated its transmission via ticks. Another American, William Welch, isolated the gas gangrene bacillus at his laboratory at John Hopkins University. Walter Reed led a contingent to Cuba and pinpointed mosquitoes as the insects involved in yellow fever transmission. In addition, Winogradsky and Beijerinck began examining the role of non-infectious microorganisms in the soil and reported that microorganisms play an important role in nitrogen, sulphur and carbon cycling as well as process of nitrogen fixation by symbiotic or free living soil bacteria. Iwanowsky and Beijerinck provided the first evidence for virus as infectious agent. The advent of World War I in 1914 signaled a dramatic pause in microbiology research and brought to an end the Golden Era of Microbiology. The era of chemotherapy and microbial genetics Paul Ehrlich in collaboration with Sakahiro Hata, discovered the drug, Salvarsan, an arsenobenzol compound in 1910 for the treatment of syphilis caused by Treponema pallidum. Ehrlich laid important foundation of the era of chemotherapy which is defined as the use of chemicals that selectively inhibit or kill pathogens without causing damage to the victim. Gerhard Domagk of Germany in 1935 reported that Prontosil, a red dye used for staining leather, was active against pathogenic streptococci and staphylococci in mice even though it had no effect against the same infectious agent in the test tube. The two French scientists Jacques and Therese Trefonel in the same year showed that the compound Prontosil was broken down within the body of the animal to sulphanilamide (sulpha drug) which was the true active factor. Domagk was awarded Nobel Prize in 1939 for the discovery of the first sulpha drug. The credit for the discovery of the first”wonder drug”, penicillin goes to a Scottish physician and bacteriologist, Sir Alexander Fleming (Microfocus 1.7) in 1929 from the mold Penicillium notatum. Fleming discovered the first antibiotic which is a microbial product that can kill susceptible microorganisms and inhibit their growth. Sir Howard. W. Florey and Ernst B. Chain at Oxford University in 1941 developed methods for industrial production of penicillin in England. Fleming, Florey and Chain shared the Nobel Prize in 1945 for the discovery and production of penicillin. SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY 17 MICROFOCUS 1.7 Alexander Fleming, a Scottish, was born in the year 1881. He was a physician by training, but spent most of his time studying bacteria. Sir Alexander Fleming, in 1922 discovered that lysozyme, an enzyme found in tears, saliva and sweat, could kill bacteria, the first body secretion shown to have chemotherapeutic properties. He in 1928 discovered the first antibiotic (Gr. anti-against + bios- life, the microbial product that can kill susceptible microorganisms or inhibit their growth), penicillin. In 1929, Alexander Fleming published his findings in the paper describing penicillin and its effect on Gram-positive bacteria. Fleming died in 1955, at the age seventy-four. Alexander Fleming (1881–1955) At the time of World War II (1939–44), S. A. Waksman of Rutgers’ University, USA discovered another antibiotic, streptomycin along with Albert Schatz in 1944 from an actinomycete, Streptomyces griseus. Waksman received the Nobel Prize in 1952 for his notable contribution and for the discovery of streptomycin used in the treatment of tuberculosis, a bacterial disease caused by Mycobacterium tuberculosis, that had been discovered by Robert Koch in 1882. Dr. Paul R. Burkholder in 1947 isolated chloramphenicol (chloromycetin) from Streptomyces venezuelae. Dr. B.M. Dugger in 1948 identified aureomycin from Streptomyces aureofaciens and terramycin was discovered by Finlay, Hobby and collaborators in 1950 from Streptomyces rimosus. Antibiotic production continues to be the important area of industrial research. Currently, there are over 8000 antibiotics known, of which only a few are being used as chemotherapeutic agents. In 1943, Italian microbiologist Salvador Luria and the German physicist Max Dulbriick carried out a series of experiments with bacteria and viruses. They used the bacterium Escherichia coli to address a basic question regarding the nature of mutations, spontaneous or induced. Luria and Dulbriick showed that bacteria could develop spontaneous mutations that generate resistance to viral infection. Besides the significance of their findings to microbial genetics, their use of E. coli as a microbial model system showed to other researchers that these relatively simple microorganisms could be used to study general principles of biology. The experiments carried out by Americans George Beadle and Edward Tatum, using the fungus, Neurospora, showed that one gene codes for one enzyme i.e., one-gene oneenzyme hypothesis. Oswald Avery, Colin Mcleod, and Maclyn McCarty, working with the bacterium Streptococcus pneumoniae, suggested that deoxyribonucleic acid (DNA) is the genetic material in cells. In 1953, American biochemist Alfred Hershey and geneticist Martha Chase, using bacterial viruses, provided irrefutable evidence that DNA is the substance of genetic material. Joshua Lederberg (Microfocus 1.8) in 1958 received the Nobel Prize in Physiology or Medicine for his discoveries concerning genetic recombination and organization of genetic material in bacteria. The small size of bacteria hindered scientists’ abilities to confirm that bacteria were “cellular” in function. In the 1940s and 1950s, an electron microscope was developed that could magnify objects and cells thousands of times more than typical light microscopes. With the electron microscopes, for the first time bacteria were seen as being cellular like all other microbes, plants and animals. However studies showed that they were organized in a fundamentally different way from other organisms. It was shown that animal and plant cells contained a cell nucleus that stores the genetic information in the form of chromosomes and was separated physically from other cell structures by a membrane 18 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY envelope. This type of cellular organization is called eukaryotic (eu= true+karyon = kernel, nucleus). Microscopic observations of the Protista and Fungi had revealed that these organisms also had a eukaryotic organization. MICROFOCUS 1.8 Dr. Joshua Lederberg was born on May 23, 1925 in Montclair, New Jersey. Joshua Lederberg is noted for two landmark discoveries in bacterial genetics: bacterial conjugation and transduction, both laying foundations for genetic engineering, modern biotechnology and genetic approaches to medicine. Interdisciplinary in his scientific interests and methods, he became a pioneer of Exobiology and the exploration of space, and was instrumental in introducing computers and artificial intelligence into laboratory research and biomedical communication. Lederberg, along with Beadle and Tatum, was awarded the Nobel Prize at the age 33, for his discoveries concerning genetic recombination and organization of the genetic material of bacteria. In addition to receiving the Nobel Prize, Lederberg has received many other awards and honours. It can only be said that Joshua Lederberg single-handedly changed the nature of bacterial genetics and changed the course of both genetics and biochemistry. Dr. Joshua Lederberg Studies with the electron microscope revealed that bacterial cells had few of the cellular structures typical of eukaryotic cells. They lacked a cell nucleus, indicating the bacterial chromosome was not surrounded by a membrane envelope. Therefore, bacteria have a prokaryotic (pro= primitive + karyon = nucleus) type of cellular organization. Eubacteria and Archaea, thus, are prokaryotes. The modern molecular biology era By the 1970s, research on bacterial physiology, biochemistry and genetics had advanced to such an extent that it was possible to experimentally manipulate the genetic material of living organisms. With the invention of restriction enzymes, it became possible to introduce DNA from foreign sources into bacteria and control its replication. This led to the development of fascinating field of Biotechnology. In 1967, Carl Woese (Microfocus 1.9) originated the RNA World Hypothesis and also discovered the extremophiles, Archaea. Prof Har Gobind Khorana (Microfocus 1.10) along with Nirenberg and other coworker deciphered the genetic code and was awarded the Nobel Prize in 1968. Many diseases that were previously thought to have only behavioural or genetic components have been found to involve microorganisms. MICROFOCUS 1.9 Carl Woese, an American microbiologist, was born on July 15, 1928 in Syracuse, New York. He is famous for defining the Archaea (a new domain or kingdom of life) in 1977 by phylogenetic analysis of 16S ribosomal RNA, a technique pioneered by Woese and which is now standard practice. He is also the originator of RNA World Hypothesis in 1967, although not by name. Carl Woese SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY 19 Two Australians, Barry J. Marshall and Robin Warren won the 2005 Nobel Prize for showing that bacterial infections of Helicobacter pylori (= Campylobacter pylori) and not the stress, is responsible for painful ulcers in the stomach and intestine.The 1982 discovery transformed peptic ulcer disease from a chronic, frequently disabling condition to one that can be cured by a short regimen of antibiotics and medicines. MICROFOCUS 1.10 Prof. Har Gobind Khorana was born on 2nd January, 1922 in Rajpura, Punjab, India. He was awarded the Nobel Prize in Physiology/Medicine in 1968 for his contribution to the elucidation of the genetic code. His research explained how messages inscribed in genes are translated into proteins. He was also the first person to successfully synthesize a gene in 1970. This achievement established the foundation for the Biotechnology industry. The proteomics is defined as where custom-designed genes are being widely used to engineer new plants and animals. Prof. H.G. At the same time, nucleic acid sequencing methods were developed which left its impact in all the areas of biology. Sequencing technology helped microbiologists to reveal phylogenetic (evolutionary) relationships among prokaryotes, which led to evolutionary new concepts in the field of biological classification. The field of Genomics is also a contribution of sequencing technology, in which the comparative analysis of the genes of different organisms is carried out. The huge amounts of genomic information now in hand are leading to major advances in medicine, microbial ecology, industrial microbiology, and many other areas of biology. The genomics era has given birth to a new subdiscipline, Proteomics. The proteomics is defined as the study of protein expression in cells. The significance of such developments in molecular biology to all of biology is understood by the fact that numerous Nobel Prizes have been awarded to researchers for their work in this field as shown in the table 1.10. Table 1.10: Nobel Laureates in Physiology or Medicine since 1901 Year Investigator(s) Discovery 1901 Emil von Behring Serum therapy, especially its application against diphtheria 1902 Ronald Ross Malaria, by which he has shown how it enters the organism 1903 Niels Ryberg Finsen Treatment of diseases, especially lupus vulgaris, with concentrated light radiation 1904 Ivan Pavlov Physiology of digestion 1905 Robert Koch Investigations and discoveries in relation to tuberculosis 1906 Camillo Golgi and Santiago Structure of the nervous system Ramony Cajal 1907 Alphonse Laveran Role played by protozoa in causing diseases 1908 Ilya Metchnikoff and Work on immunity Paul Ehrlich (Contd.) 20 Year 1909 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY Investigator(s) Theodor Kocher Discovery Physiology, pathology and surgery of the thyroid gland 1910 Albrecht Kossel Cell chemistry, work on proteins, including the nucleic substances 1911 Allvar Gullstrand Dioptrics of the eye 1912 Alexis Carrel Vascular suture and the transplantation of blood vessels and organs 1913 Charles Richet Anaphylaxis 1914 Robert Bárány Physiology and pathology of the vestibular apparatus 1919 Jules Bordet Discoveries relating to immunity 1920 August Krogh Capillary motor regulating mechanism 1922 Archibald V. Hill and Otto Meyerhof Discovery relating to the production of heat in the muscle (Hill) and discovery of the fixed relationship between the consumption of oxygen and the metabolism of lactic acid in the muscle (Meyerhof) 1923 Frederick G. Banting Discovery of insulin and John Macleod 1924 Willem Einthoven Mechanism of the Electrocardiogram 1926 Johannes Fibiger Discovery of the Spiroptera carcinoma 1927 Julius Wagner-Jauregg Therapeutic value of malaria inoculation in the treatment of dementia paralytica 1928 Charles Nicolle Work on typhus 1929 Christiaan Eijkman and Sir Frederick Hopkins Discovery of the antineuritic vitamin (Eijkman) and discovery of the growth stimulating vitamins (Hopkins) 1930 Karl Landsteiner Discovery of human blood groups 1931 Otto Warburg Nature and mode of action of the respiratory enzyme 1932 Sir Charles Sherrington Functions of neurons and Edgar Adrian 1933 Thomas H. Morgan Role played by the chromosome in heredity 1934 George H. Whipple, Liver therapy in cases of anaemia George R. Minot and William P. Murphy 1935 Hans Spemann Organizer effect in embryonic development 1936 Sir Henry Dale and Otto Loewi Chemical transmission of nerve impulses 1937 Albert Szent-Györgyi Biological combustion processes, with special reference to vitamin C and the catalysis of fumaric acid 1938 Corneille Heymans Role played by the sinus and aortic mechanisms in the regulation of respiration 1939 Gerhard Domagk Discovery of the antibacterial effect of prontosil 1943 Henrik Dam and Discovery of vitamin K and study on the chemical nature of Edward A. Doisy vitamin K (Contd.) SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY Year Investigator(s) 1944 Joseph Erlanger and 21 Discovery Highly differentiated functions of single nerve fibres Herbert S. Gasser 1945 Sir Alexander Fleming, Ernst B. Chain and Sir Howard Florey Discovery of penicillin and its curative effect in various infectious diseases 1946 Hermann J. Muller Production of mutations by means of X-ray irradiation 1947 Carl Cori, Gerty Cori and Bernardo Houssay Discovery of the course of the catalytic conversion of glycogen (Cori and Cori) and discovery of the part played by the hormone of the anterior pituitary lobe in the metabolism of sugar (Bernardo Houssay) 1948 Paul Müller High efficiency of DDT as a contact poison against several arthropods 1949 Walter Hess Discovery of the functional organization of the interbrain as a and Egas Moniz coordinator of the activities of the internal organs (Walter Hess) and discovery of the therapeutic value of leucotomy in certain psychoses (Egas Moniz) Edward C. Kendall, Tadeus Reichstein Hormones of the adrenal cortex, their structure and biological effects 1950 and Philip S. Hench 1951 Max Theiler Yellow fever and how to combat it 1952 Selman A. Waksman Discovery of streptomycin, the first antibiotic effective against tuberculosis 1953 Hans Krebs and Fritz Lipmann Discovery of the citric acid cycle and discovery of co-enzyme A and its importance for intermediary metabolism 1954 John F. Enders, Thomas H. Weller and Frederick Ability of poliomyelitis viruses to grow in cultures of various types of tissue C. Robbins 1955 Hugo Theorell Nature and mode of action of oxidation enzymes 1956 André F. Cournand, Werner Forssmann and Dickinson W. Richards Heart catheterization and pathological changes in the circulatory system 1957 Daniel Bovet Discoveries relating to synthetic compounds that inhibit the action of certain body substances, and especially their action on the vascular system and the skeletal muscles 1958 George Beadle, Edward Tatum, and Joshua Lederberg Genes act by regulating definite chemical events (Beadle and Tatum) and discoveries concerning genetic recombination and the organization of the genetic material of bacteria (Lederberg) 1959 Severo Ochoa and Arthur Kornberg Mechanisms in the biological synthesis of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) 1960 Sir Frank Macfarlane Burnet and Peter Medawar Acquired immunological tolerance 1961 Georg von Békésy Physical mechanism of stimulation within the cochlea (Contd.) 22 Year A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY Investigator(s) Discovery 1962 Francis Crick, James Watson and Maurice Wilkins Molecular structure of nucleic acids and its significance for information transfer in living material 1963 Sir John Eccles, Alan L. Hodgkin and Andrew F. Huxley Ionic mechanisms involved in excitation and inhibition in the peripheral and central portions of the nerve cell membrane 1964 Konrad Bloch and Feodor Lynen Mechanism and regulation of the cholesterol and fatty acid metabolism 1965 François Jacob, André Genetic control of enzyme and virus synthesis L woff and Jacques Monod 1966 Peyton Rous and Charles Brenton Huggins Discovery of tumour inducing viruses (Rous) and discoveries concerning hormonal treatment of prostatic cancer (Huggins) 1967 Ragnar Granit, Haldan K. Primary physiological and chemical visual processes in the eye Hartline and George Wald 1968 Robert W. Holley, H. Gobind Khorana and Marshall Interpretation of the genetic code and its function in protein synthesis W. Nirenberg 1969 Max Delbrück, Alfred D. Hershey and Salvador E. Luria Replication mechanism and genetic structure of viruses 1970 Sir Bernard Katz, Ulf von Euler and Julius Axelrod Humoral transmittors in the nerve terminals and the mechanism for their storage, release and inactivation 1971 Earl W. Sutherland, Jr. Mechanisms of the action of hormones 1972 Gerald M. Edelman and Chemical structure of antibodies Rodney R. Porter 1973 Karl von Frisch, Konrad Lorenz and Nikolaas Tinbergen Organization and elicitation of individual and social behaviour patterns 1974 Albert Claude, Christian de Duve and George E. Palade Structural and functional organization of the cell 1975 David Baltimore, Renato Interaction between tumour viruses and the genetic material Dulbecco, and Howard of the cell M. Temin 1976 Baruch S. Blumberg and New mechanisms for the origin and dissemination of D. Carleton Gajdusek infectious diseases 1977 Roger Guillemin, Andrew V. Schally and Rosalyn Yalow Discoveries concerning the peptide hormone production of the brain (Roger and Andrew) and for the development of radioimmunoassays of peptide hormones (Rosalyn) 1978 Werner Arber, Daniel Nathans and Discovery of restriction enzymes and their application to problems of molecular genetics Hamilton O. Smith (Contd.) SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY Year Investigator(s) 23 Discovery 1979 Allan M. Cormack and Godfrey N. Hounsfield Development of computer assisted tomography 1980 Baruj Benacerraf, Jean Dausset and George D. Snell Genetically determined structures on the cell surface that regulate immunological reactions 1981 Roger W. Sperry, David H.Hubel, Torsten Discoveries concerning the functional specialization of the cerebral hemispheres (Roger) and for discoveries concerning N. Wiesel information processing in the visual system (Hubel and Wiesel) Sune K. Bergström, Bengt I. Samuelsson and Prostaglandins and related biologically active substances 1982 John R. Vane 1983 Barbara McClintock Discovery of mobile genetic elements 1984 Niels K. Jerne, Georges J.F. Köhler, Theories concerning the specificity in the development and control of the immune system and the discovery of the principle César Milstein 1985 Michael S. Brown and for production of monoclonal antibodies Regulation of cholesterol metabolism Joseph L. Goldstein 1986 Stanley Cohen and Discoveries of growth factors Rita Levi-Montalcini 1987 Susumu Tonegawa Genetic principle for generation of antibody diversity 1988 Sir James W. Black, Gertrude B. Elion and George H. Hitchings Important principles for drug treatment 1989 J. Michael Bishop and Cellular origin of retroviral oncogenes Harold E. Varmus 1990 Joseph E. Murray and E. Donnall Thomas Organ and cell transplantation in the treatment of human disease 1991 Erwin Neher and Bert Sakmann Function of single ion channel in cells 1992 Edmond H. Fischer and Edwin G. Krebs Reversible protein phosphorylation as a biological regulatory mechanism 1993 Richard J. Roberts and Phillip A. Sharp Split genes 1993 Kary Mullis Invention of the polymerase chain reaction (PCR) 1993 Hamilton Smith Specificity of action of restriction enzymes to splice foreign components into DNA 1994 Alfred G. Gilman and Martin Rodbell G-proteins and their role in signal transduction in cell 1995 Edward B. Lewis, Christiane NüssleinVolhard and Eric F. Wieschaus Genetic control of early embryonic development (Contd.) 24 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY Year Investigator(s) Discovery 1996 Peter C. Doherty and Rolf M. Zinkernagel Specificity of the cell mediated immune defence 1997 Stanley B. Prusiner Discovery of prions 1998 Robert F. Furchgott, Louis J. Ignarro and Ferid Murad Nitric oxide as a signaling molecule in the cardiovascular system 1999 Günter Blobel Proteins have intrinsic signals that govern their transport and localization in the cell 2000 Arvid Carlsson, Paul Greengard and Eric R. Kandel Signal transduction in the nervous system 2001 Leland H. Hartwell, Tim Hunt and Sir Paul Nurse Key regulators of the cell cycle 2002 Sydney Brenner and H. Robert Horvitz and John E. Sulston Genetic regulation of organ development and programmed cell death 2003 Paul C. Lauterbur and Sir Peter Mansfield Magnetic resonance imaging (MRI) 2004 Richard Axel and Linda B. Buck Odorant receptors and the organization of the olfactory system 2005 Barry J. Marshall and J. Robin Warren Discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease 2006 Andrew Z. Fire and Craig C. Mello RNA interference, gene silencing by double-stranded RNA 2007 Mario Capecchi, Oliver Smithies and Martin Evans Gene targeting on knockout mouse using embryonic stem cells and in understanding gene disease relationship Basic and applied sciences in microbiology Microbiology, that has played a major role in the advancement of human health and welfare, is one of the largest and most complex of the biological sciences as it deals with many diverse biological disciplines. In addition to studying the natural history of microbes, it also deals with every aspect of microbe-human and environmental interaction. These interactions include: ecology, genetics, metabolism, infection, disease, chemotherapy, immunology, genetic engineering, industry and agriculture. The branches that come under the large and expanding umbrella of microbiology are categorized into basic and applied disciplines. The categorization is given below in the Table 1.11. Table 1.11: Basic and applied disciplines in microbiology Discipline A. Basic disciplines Algology or Phycology Nature of study Study of algae-simple aquatic organisms ranging from single-celled forms to large seaweeds. (Contd.) SCOPE AND HISTORICAL DEVELOPMENTS IN MICROBIOLOGY Discipline 25 Nature of study Bacteriology Study of bacteria—the smallest, simplest, single-celled prokaryotic microorganisms and archaea – prokaryotic microorganisms which constitute an ancient group intermediate between the bacteria and eukaryotes. Mycology Microbial Genetics Study of fungi – microscopic eukaryotic forms (molds and yeasts), higher forms (mushrooms, toadstools and puffballs), and slime molds. Study of protozoans—animal like and mostly single-celled, eukaryotic organisms. Study of viruses (infectious agents containing either DNA or RNA that require living cells for their replication/ or reproduction) and viral diseases. Study of parasitism and parasites that include pathogenic protozoa, helminth worms and some insects. Study of interrelationships between microbes and environment. Study of detailed structures of microorganisms. Classification, naming, and identification of microorganisms and constructions of the phylogenetic tree of life. Metabolism of microbes at the cellular and molecular levels. Study of discovery of microbial enzymes and the chemical reactions carried out by them. Study of genome (i.e., genomics) of microorganisms and construction of phylogenetic tree based on rRNA. Study of heredity and variation in varieties. Molecular Biology The advanced study of the genetic material (DNA, RNA) and protein synthesis. Protozoology Virology Parasitology Microbial Ecology Microbial Morphology Microbial Systematics Microbial Physiology Microbial Biochemistry Molecular Microbiology B. Applied disciplines Immunology Agricultural Microbiology Food Microbiology Dairy Microbiology Industrial Microbiology Marine Microbiology Air Microbiology Exomicrobiology Diagnostic Microbiology The immune system that protects against infections and attempts to understand the many phenomena that are responsible for both acquired and innate immunity, in addition to the study of antibody-antigen reactions in the laboratory. Study of relationships of microbes and crops with an emphasis on control of plant diseases and improvement of yields. Interaction of microorganisms and food in relation to food bioprocessing, food spoilage, food borne diseases and their prevention. Production of and maintenance in quality control of dairy products. Industrial uses of microbes in the production of alcoholic beverages, vitamins, amino acids, enzymes, antibiotics and other drugs. Study of microorganisms and their activity concerning human and animal health in fresh, estuarine and marine waters. Role of aerospora in contamination and spoilage of food and dissemination of plant and animal diseases through air. Exploration for microbial life in outer space. Fundamental principles and techniques involved in the study of pathogenic organisms as well as their application in the diagnosis of infectious diseases. Epidemiology and Public Health Microbiology Monitoring, control and spread of diseases in communities. Biotechnology The scientific manipulation of living organisms, especially at the molecular and genetic level to produce useful products. 26 A TEXTBOOK OF BASIC AND APPLIED MICROBIOLOGY The new frontiers The long span of four hundred and fifty years of microbiology has brought amazing insight into the biology of microorganisms and has also brought with it new challenges, which have both positive and negative effects upon the society. Diseases like AIDS, Bird’s flu and SARS seem to appear without a trace and have challenged the basic understanding of microbial diseases. On the other hand, new discoveries have opened a door for understanding how a cell works at the most fundamental level, and newly discovered bacteria stretch the already overwhelming picture of microbial diversity. Microbial ecology is providing new clues to the roles of microorganisms in the environment. Biofilms are recognized as the dominant form of organization of microbial communities. The vast number of unculturable microbes can be studied and characterized with genomic tools. The understanding of microbial evolution has advanced with the use of genomic technologies and has provided new perspectives on the relationships between microorganisms. Microorganisms play more positive roles than simply causing infectious diseases. The majority of microbes are seen as rulers of the world because of their essential and important beneficial roles that can provide humanity with an even better and more healthful existence. REVIEW QUESTIONS 1. Define microbiology. Enlist the various basic and applied areas of microbiology. 2. Why was the abandonment of the spontaneous generation theory so significant? Using the scientific method, describe the steps you would take to test the theory of spontaneous generation. 3. Which early microbiologist was the most responsible for developing sterile laboratory techniques? 4. Which scientist is the most responsible for finally laying down the theory of spontaneous generation to rest? 5. Enlist the contributions of Antony van Leeuwenhoek, Edward Jenner, Joseph Lister, Louis Pasteur, Robert Koch and Joshua Lederberg. 6. What are the recent developments in the field of molecular microbiology? 7. List important commercial enzymes and their sources. 8. Name the scientists who first discovered Archaea? 9. What is a binomial system of nomenclature, and who proposed it? 10. Name the causative agents of: syphilis, whooping cough, blastomycosis, tinea cruris, toxoplasmosis, giardiasis and schistosomiasis. 11. What are Koch’s postulates and how did they influence the development of microbiology? 12. How did Metchnikoff contribute to the development of immunology? 13. Describe the notable contributions of five scientists that resulted in the award of Nobel prizes to them in microbiology. 14. How did Ferdinand Cohn and Carl Woese contribute to bacteriology and molecular biology respectively. 15. How did Pasteur’s Swan-neck experiment defeat the theory of spontaneous generation? 16. For what contributions are Hooke, Beijerinck, and Ehrlich remembered in microbiology? 17. How did the discovery of first antibiotic take place? Name the antibiotic and that mold from which it was isolated.
