Micro-08105 3(2-1)
GENERAL MICROBIOLOGY AND IMMUNOLOGY
Dr. Shahzad Ali
Assistant Professor
Department of Wildlife and Ecology
UVAS, Ravi Campus, Pattoki

Microbiology:
The branch of biology that deals with microorganisms
 A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye)
 Commonly called “germs, viruses, agents…” but not all cause disease and many more are useful or essential for human life

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Simple, single-celled (unicellular) organisms
Prokaryotes
Several shapes (bacilli, cocci, spirilla)
Cell walls composed of a carbohydrate and protein complex called peptidoglycan
Reproduce by binary fission
Nutrition:
Most bacteria use organic chemical derived from living and dead organisms
Some photosynthetic
Other : inorganic substances
Swim: flagella

Archaea
 Archaea (ar'ke-a) consist of prokaryotic cells
 Cell walls lack peptidoglycan
 Found in extreme environments
 Three main groups
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The methanogens produce methane as a waste product from respiration
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The extreme halophiles (halo = salt; philic = loving) live in extremely salty environments such as the Great Salt Lake and the
Dead Sea
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The extreme thermophiles (therm = heat) live in hot sulfurous water, such as hot springs at Yellowstone National Park
 None pathogenic for humans

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Yeast: unicellular
Mold: compose of long filaments (hyphae)
Mushrooms: none photosynthetic
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 Nourishment by absorbing solutions of organic material from their environment- whether soil, seawater, fresh water, or an animal or plant host

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Single-celled eukaryotes
Similar to animals in nutrient needs and cellular structure
Live freely in water; some live in animal hosts
Asexual (most) and sexual reproduction
Most are capable of locomotion by
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Pseudopodia – cell extensions that flow in direction of travel
Cilia – numerous, short, hairlike protrusions that propel organisms through environment
Flagella – extensions of a cell that are fewer, longer, and more whiplike than cilia

 Unicellular or multicellular
 Photosynthetic
 Sexual and asexual reproduction
 Categorized on the basis of pigmentation, storage products, and composition of cell wall (mostly cellulose)
 Examples ( class activity )

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Acellular
Reproduce inside host
Viruses are very small and they measured in nanometers.
They can only be seen with an electron microscope.
They are composed of a core of
DNA or RNA surrounded by a protein coat
Their size ranges from 20 nanometers to 250 nanometers.

A Brief History of Microbiology
Importance of observations made by Hooke and van Leeuwenhoek
 Robert Hooke observed that
 cork was composed of boxes“
; he introduced the term cell (1665)
Hooke's observations laid the ground
 work for development of the cell theory , the concept that all living things are composed of cells
What is cell theory? ( Class Activity )

A Brief History of Microbiology
 Anton van Leeuwenhoek,
(using a simple microscope, was the first to observe microorganisms
(1673).

A Brief History of Microbiology
The Debate over Spontaneous Generation
 Initially people commonly believed that
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Toads, snakes, and mice could be born of moist soil
Flies could emerge from manure; and
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Maggots, the larvae of flies, could arise from decaying corpses
 Redi’s Experiments (1668)
 opponent of spontaneous generation
 When decaying meat was kept isolated from flies, maggots never developed
 Meat exposed to flies was soon infested
 As a result, scientists began to doubt Aristotle’s theory

A Brief History of Microbiology
 John Needham (1745)
 Heated nutrient fluids before pouring them into covered flasks, the cooled solutions were soon teeming with microorganisms
 Microbes developed spontaneously from the fluids
 Lazzaro Spallanzani (1765)
 Microorganisms from the air probably had entered Needham's solutions after they were boiled
 Spallanzani showed that nutrient fluids heated after being sealed in a flask did not develop microbial growth
 Needham responded by claiming the " vital force
" necessary for spontaneous generation had been destroyed by the heat and was kept out of the flasks by the seals.

A Brief History of Microbiology
Anton Laurent Lavoisier
 Showed the importance of oxygen to life.
 Spallanzani's observations were criticized on the grounds that there was not enough oxygen in the scaled flasks to support microbial life
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Rudolf Virchow
 Challenged the case for spontaneous generation with the concept of biogenesis
 The claim that living cells can arise only from preexisting living cells

A Brief History of Microbiology
Pasteur’s Experiments (1861)
 Spontaneous generation disproved by a series of experiments
 Microorganisms arc present in the air
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can contaminate sterile solutions
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but that air itself docs not create microbes
 When the “swan-necked flasks” remained upright, no microbial growth appeared
 When the flask was tilted, dust from the bend in the neck seeped back into the flask and made the infusion cloudy with microbes within a day

Pasteur’s Experiments

A Brief History of Microbiology
 Pasteur's discoveries led to
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The development of aseptic techniques* used in laboratory and medical procedures to prevent contamination by microorganisms
Aseptic techniques
 Techniques that prevent contamination by unwanted microorganisms, which are now the standard practice in laboratory and many medical procedures

A Brief History of Microbiology
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The Golden Age of Microbiology
The science of microbiology advanced rapidly between 1857 and 191 4
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Fermentation
Pasteurization
Germ theory
Vaccination
Etc. (see figure 1.4
and Table 1.2
for detail)
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CLASS AVTIVITY
Summarize in your own words the germ theory of disease. 1-8
What is the importance of Koch's postulates? 1-9
What is the significance of Jenner's discovery? 1-10

 The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
 The microorganism must be isolated from a diseased organism and grown in pure culture .
 The cultured microorganism should cause disease when introduced into a healthy organism.

A Brief History of Microbiology
The Birth of Modern Chemotherapy:
(Dreams of a "Magic Bullet“)
 Chemotherapy is the chemical treatment of a disease
 Two types of chemotherapeutic agents
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Synthetic drugs (chemically prepared in the laboratory)
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Antibiotics (substances produced naturally by bacteria and fungi to inhibit the growth of other microorganisms)
 Paul Ehrlich introduced an arsenic-containing chemical called salvarsan to treat syphilis (1910)

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Alexander Fleming observed that the Penicillium fungus inhibited the growth of a bacterial culture. He named the active ingredient penicillin (1928) .
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Penicillin has been used clinically as an antibiotic since the
1940s.
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Researchers arc tackling the problem of drug-resistant microbes

 New branches of microbiology were developed
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Bacteriology.
the study of bacteria
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Mycology, the study of fungi, includes medical, agricultural, and ecological branches
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Parasitology is the study of protozoa and parasitic worms
Immunology, the study of immunity, actually dates back in Western culture to Jenner's first vaccine in 1796
Virology , The study of viruses

Recombinant DNA Technology
 Microorganisms can now be genetically modified to manufacture large amounts of human hormones and other urgently needed medical substances
Origins in two related fields
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The first, microbial genetics , studies the mechanisms by which microorganisms inherit traits
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The second, molecular biology , specifically studies how genetic information is carried in molecules of DNA and how DNA directs the synthesis of proteins