Introduction to
Microbiology
Dr. Carmen Rexach
Mt San Antonio College
Microbiology
What are microbes?
Three empires
BACTERIA
EUKARYA
ARCHAEA
Microbes include:
• Bacteria
– Kingdom Prokaryotae (Monera)
– Kingdom Archaea
• Protozoans
– Kingdom Protista
• Fungi
– Kingdom Fungi
• Algae
– Kingdom Protista or Plantae
• Multicellular parasites
– Kingdom Animalia
Characteristics of life
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Nutrition (self-feeding)
Self-replication (growth)
Differentiation
Chemical Signaling (response to stimuli)
Evolution (natural selection)
Viruses will also be discussed….but they aren’t considered to be
alive, even though we classify them as microbes!
The role of microbes
• Decomposers, nutrient recycling
Clover root with Rhizobium nodules
The role of microbes: commercial uses
• Synthesis of chemical products
• Foods
• Agriculture
Commercial uses
• Biotechnology
Bioreactor and vaccine production
Commercial uses
• Bioremediation
Even though most
microbes are harmless
and are important
contributors to a healthy
world, we tend to
associate them most
often with disease!
Pathogen: Parasite that does harm to the host
Emerging infectious diseases
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Tuberculosis
Hepatitis C
Malaria
Enterohemorrhagic E. coli (0157:H7)
Lyme Disease
Influenza
Hantavirus pulmonary syndrome
AIDS
CJD/BSE
Nipah virus
Foot and Mouth Disease
West Nile Virus
SARS
Zika virus
Why are infectious
diseases still a problem
today?
Bacteria are ubiquitous
• Aseptic technique: exclude
contaminants, prevent accidental
inoculation of ourselves and others
• Try to minimize airborne contaminants
HISTORY OF
INFECTIOUS DISEASE
AND GERM THEORY
Ancient History
• Association between
sanitation and disease
– First toilets on Crete,
India, Pakistan, Scotland
2800 BC
– Rome: Public lavatories with
running water AD 315
– Chinese invented toilet
paper in AD 589
– Punishment for pollution of
water supply in ancient
Rome was death
Ancient History
• Recognition that some diseases were
communicable
– Shunning of lepers
– Abandonment of communities during plague
epidemics
– Recognition that previously infected individuals
did not get disease again
– Biblical rules and regulations for disposal of human
waste
– Malaria – Pontine marshes
• The leper who has the disease shall wear torn clothes and let
the hair of his head hang loose, and he shall cover his upper
lip and cry, `Unclean, unclean.' He shall remain unclean as long
as he has the disease; he is unclean; he shall dwell alone in a
habitation outside the camp.
– Leviticus 13: 45-56
AD 300 first accurate description of
leprosy by Sursuta, an Indian physician
History
• Hieronymus Fracastorius (1483-1553) from Verona
– Trained in medicine, geology, philosophy
– De Contagione
• described seeds of disease
• Could be spread by direct contact, fomites,
distance (air and water)
• This was first proposal of germ theory, 300 years
before it was formulated by Pasteur and Koch!
Invention of the microscope
• Robert Hooke (1665)
– Cells= smallest units of life
– Beginning of cell theory
Robert
Hooke
Invention of microscope
• Anton von Leewenhoek (1673-1723)
– Magnifying lenses
– Animalcules
• Bacteria from teeth
– Believed they arose from rotting gums
• Sperm, Giardia
– Royal Society of London
Spontaneous generation:
debate
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Francesco Redi (1626-97)
John Needham (1745)
Lazzaro Spallanzani (1729-1799)
Rudolf Virchow (1858)
Louis Pasteur (1822-95)
Sequence of events
• Francesco Redi
– Maggots and raw meat
– “Omne vivum ex ovo”
• John Needham
– Boiled broth left open to the
environment generates microbes
• Lazzaro Spallanzani
– Sealed flasks produced no
microbes: disputed Needham’s
findings
Needham and Laurent Lavoisier respond: there can be no
life without oxygen!
Sequence of events
• Rudolf Virchow (18211902)
– German pathologist
– Biogenesis = “omni cellula
a cellula”
– Published in 1858
– Did not believe in germ
theory
Louis Pasteur (1822-1895)
• Swan-necked flask
• Basis of aseptic technique
John Tyndall
• Supported Pasteur’s position against
spontaneous generation
• Spores
• Developed “tyndalization”
– Heating media to bp at normal atmospheric
pressure over successive days to destroy
spores
– Useful when autoclave is unavailable
The presence of spores in Pasteur’s experiment would have given him entirely
different results! Great discoveries are often the results of LUCK!
Golden Age of
Microbiology (1857-1914)
• Beginning with Pasteur’s work,
discoveries included the relationship
between microbes and disease,
immunity, and antimicrobial drugs
Golden Age of Microbiology
• Fermentation and pasteurization
– Pasteur
• Merchants concerned about beer/wine
spoilage
• Fermentation= anaerobic process;
spoilage caused by aerobic bacteria
• Developed heat pasteurization
– Vat temperatures raised to 60oC
– Pasteurization
• Still used today!
• What happened when E.coli 0157:H7 was
found at Odwalla?
Louis Pasteur
Germ theory of disease
• People used to think that diseases
were a punishment
• How did we determine that there was
link between microbes and disease?
Germ theory
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Agostino Bassi (1835)
Ignaz Semmelweis (1840)
Joseph Lister (1860)
Robert Koch (1876)
Agostino Bassi (1835)
• Italian entomologist
• Determined cause of a
silkworm disease by
using the microscope
and observing fungus
• Set the stage for
Pasteur’s discovery of
protozoal agent of
another silkworm
disease
Ignaz Philip Semmelweiss
(1818-65)
• Assistant at First
Obstetric Clinic,
Allgemeines
Krankenhaus, Vienna
• Clinics training
physicians had higher
rate of puerpural fever
than those training
nurse midwives…why?
Semmelweiss and handwashing
Putrid
particles
physicians
midwives
Dissecting
room
dinner
Joseph Lister (1827-1912)
• Professor of
Surgery, Glasgow
Royal Infirmary
• Used phenol (carbolic
acid) to sterilize
surgical wounds
• Demonstrated that
microbes caused
wound infections
Robert Koch (1843-1910)
• Received MD 1862
• Started by studying
anthrax in cattle/sheep
• Enormous contributions
to microbiology
• Winner Nobel Prize
1905 in Physiology and
Medicine
Koch’s contributions
• Demonstrated association between disease
and microbes
• Established importance of lab cultures
• Concept of pure culture
• Specific organisms had specific effects
• Discovered M. tuberculosis & developed
acid-fast stain
• Discovered V. cholera & method for ID in
water
• First photomicrographs of bacteria
Pure culture
• Developed methods via single colonies
on solid medium
• Specific size, shape, color of each
colony
• Fannie Hess and agar
– Wife of graduate student
• Julius R. Petri and the Petri dish
Koch’s postulates
• Koch’s postulates
– 1. Organism should be constantly present in
diseased animal and not in the healthy
– 2. Must be able to isolate organism in pure
culture
– 3. Inoculation of healthy animal with culture
must initiate disease symptoms
– 4. Must be able to reisolate organism from
experimental animals, culture, and again see
same organism
Edward Jenner (1749-1823)
• British physician
developed small pox
vaccine 70 years before
Koch
• Milkmaids and cowpox
• Cow pox blisters
inoculated into healthy
“volunteers” = immunity
• Later called vaccine
from “vacca”
Variolation
• Basis for Jenner’s vaccine
• Described by Buddhist nun
in China in AD 1022
– Grind up smallpox scabs and
blow into nose of nonimmune individual to induce
immune response
– Called variolation because
the small pox virus is called
Variola
Vaccines: Pasteur (1880-1890)
• Avirulent microbes stimulate immune
response
• Development of vaccines for anthrax,
chicken cholera, rabies
– Developed method for attenuation
Modern Chemotherapy:
synthetic drugs
• Paul Ehrlich (1854-1915)
– German doctor doing
research on aniline dyes
– Looking for magic bullet to
selectively target microbes
• First drug: salvarsan (for
syphillis)
• Later developed “neosalvarsan”
• These were sulfa drugs, used
extensively in the 1930’s
Antibiotics
• Alexander Fleming
(1881-1955)
– Scottish doctor
– Contaminated culture plates
left unattended
– Inhibition of bacterial growth
– Isolated Penicillium notatum
• Unaware of applications
• Renee Dubois (1939)
– Discovered Gramicidin,
tyrocidine
– Kindled interest in applications
for penicillin
Today: Problems of resistance
Modern Developments in
Microbiology
• Bacteriology = study of bacteria.
• Mycology = study of fungi.
• Parasitology = study of protozoa and
parasitic worms.
• Genomics provide tools for
reclassifying microorganisms
Modern Developments in
Microbiology
• Immunology =study of
immunity
– Vaccines and interferons to
prevent and cure viral diseases.
– Can be used for identification of
bacteria, viruses, toxins, etc.
• Serotyping (variants within a
species) proposed by Rebecca
Lancefield in 1933
• Agglutination assays
• ELISA’s
• Etc.
Figure 1.4 (3 of 3)
Modern Developments in
Microbiology
• Virology = study of viruses.
• Recombinant DNA technology
– Paul Berg (1960) produced recombinant
inserting animal DNA into bacterium producing
animal protein
– Recombinant DNA technology (genetic
engineering) involves microbial genetics and
molecular biology
Modern Developments in
Microbiology
• Using microbes
– George Beadle and Edward Tatum showed
that genes encode a cell’s enzymes
(1942).
– Oswald Avery, Colin MacLeod, and Maclyn
McCarty showed that DNA was the
hereditary material (1944).
– Francois Jacob and Jacques Monod
discovered the role of mRNA in protein
synthesis (1961).
Selected Nobel Prizes in
Physiology or Medicine
1901*
1902
1905
1908
1945
1952
1969
1987
1997
von Behring
Ross
Koch
Metchnikoff
Fleming, Chain, Florey
Waksman
Delbrück, Hershey, Luria
Tonegawa
Prusiner
Diphtheria antitoxin
Malaria transmission
TB bacterium
Phagocytosis
Penicillin
Streptomycin
Viral replication
Antibody genetics
Prions
Biological Insecticides
• Microbes used to destroy insect pests
• Bacillus thuringiensis (BT) fatal in many
insects, harmless to other animals,
including humans, and to plants.
• Remember the Taco Bell incident???
Normal microbial flora
and health
• Humans and other organisms are colonized
with bacteria
• Bacteria play a major role in health
– Colony resistance
– Stimulation of immune response
• Presence of low level cross-reactive antibodies
• Stimulate development of Peyer’s Patches
– Production of essential products
• Vitamin K & Vitamin B12