Robert Hooke first observed cells under a microscope in the 1600s and coined the term "cell". Anton van Leeuwenhoek was the first to observe bacteria and protozoa in the 1670s using single-lens microscopes. Louis Pasteur's experiments in the 1800s definitively disproved the theory of spontaneous generation and established that microorganisms are present everywhere and can contaminate previously sterile environments. Robert Koch developed methods to isolate and grow bacteria in pure culture in the late 1800s, establishing the germ theory of disease and identifying the specific bacteria that cause anthrax, cholera, and tuberculosis.
3. He observed the microscopic honeycomb
cavities in cork. Coined the term ‘’cell’’ and
published his findings in Micrographia
4. ANTON VON LEEUWENHOEK
“Father of Bacteriology”
He was the first to
observe bacteria and protozoa.
Leeuwenhoek made
microscopes consisting of a
single high-quality lens of very
short focal length.
In 1674 he observed protozoa
and bacteria and named them
as “animalcules”, he was able
to isolate from different
sources, such as rainwater,
pond and well water, and the
human mouth and intestine.
6. Spontaneous Generation (Abiogenesis)
From earliest times, people had believed and
supported spontaneous generation (abiogenesis) that living
organisms could develop from nonliving matter.
Many supported this theory.
It was Louis Pasteur who disproved the theory.
7. • Francesco Redi (1668) – Strong opponent of spontaneous
generation. He demonstrated that maggots appear on decaying
meat only when flies are able to lay eggs on the meat.
• John Needham (1745) – claimed that microorganisms could
arise spontaneously from heated nutrient broth.
• Lazzaro Spallanzani (1765) – repeated Needhams experiments
and suggested that Needham's results were due to
microorganisms in the air entering the broth.
• Rudolf Virchow (1858) – concept of biogenesis – living cells
can arise only from preexisting cells.
• Louis Pasteur (1822-1895) – Pasteur's experiments on swan
shaped necks resolved the controversy of spontaneous
generation. His discoveries led to the development of aseptic
techniques used in the laboratory and medical procedure to
prevent contamination by microorganisms that are in the air.
9. Francesco Redi's spontaneous generation experiment using jars of meat.
In the first jar, with the meat sealed inside by a stopper, maggots did not
appear on the meat;
in the second jar, covered with mesh, maggots also did not appear on the
meat;
but in the third jar, without a cover, maggots did appear on the meat and
developed into flies.
10. John Needham
Needham's experiment on spontaneous generation :
A. Needham heated the broth, let it sit uncovered for several days, then
observed microorganisms in the fluid.
B. Needham heated the broth, let it sit covered for several days, then
observed microorganisms in the fluid which may be because the cork
and flask were not sterile.
A
B
11. He boiled broth in two bottles, left one bottle open and one closed,
He found that new microorganisms appeared only in the open bottle.
His conclusion: the microorganisms entered the bottle through the air; they
were not generated spontaneously in the broth.
15. Pasteurization of milk, beer and wine. Fermentation by microorganisms
Yeast ferments sugars to alcohols and
that bacterium can oxidize the alcohol to
acetic acid.
Heating process used to kill bacteria in
some alcoholic beverages and milk.
16. Pebrine disease of silkworm brought a huge devastation to the
silkworm nurseries. His research succeeded in saving
the silk industry through a method that enabled the preservation
of healthy silkworm eggs and prevented their contamination by
the disease-causing organisms.
Germ theory of disease
states that certain diseases are caused
by the invasion of the body by
microorganisms, organisms too small to
be seen except through a microscope.
17. Joseph Lister
“Father of modern surgery”
• 1860s, the use of disinfectant to clean surgical dressings in order to
control infection in humans
• Developed a system of antiseptic surgery— designed to prevent
microorganisms from entering wounds. The approach was remarkably
successful and transformed surgery after Lister published his findings
in 1867. It also provided strong evidence for the role of microorganism
in disease because phenol, which killed bacteria, also prevented
wound infections.
19. Koch's postulates are
• 1. A specific organism should be found constantly in
association with the disease.
• 2. The organism should be isolated and grown in a pure culture
in the laboratory.
• 3. The pure culture when inoculated into a healthy susceptible
animal should produce symptoms/lesions of the same disease
• 4. From the inoculated animal, the microorganism should be
isolated in pure culture.
• 5. An additional criterion introduced is that specific antibodies
to the causative organism shouldbe demonstrable in patient's
serum.
Robert Koch (1876) proved that microorganisms transmit disease – Koch's
postulates used to prove that a particular microorganism causes a particular
disease.
21. Koch continued to improve his methods and techniques.
By solidifying liquids such as broth with gelatine and agar, for instance, he created
a solid medium for growing bacteria which was easier to handle than the liquids
used by Pasteur.( suggested by Angelina).
Koch's assistant Julius Richard Petri (1852-1921) developed the Petri dish, which
made the observation of bacteria even easier.
Introduced pure cultures
22. Isolated Mycobacterium
tuberculosis responsible
for tuberculosis (1882)
Isolated
Vibrio
cholerae
responsible
for cholera
(1883).
Isolated
Bacillus
anthracis
responsible
for anthrax
(1876).
Koch and his team also developed
ways of staining bacteria to improve
the bacteria’s visibility under
the microscope, and were able to
identify the bacterial causes
of tuberculosis, anthrax and cholera.
24. Edward Jenner
Father of Immunology
Immunity is conferred by inoculation with a vaccine.
Demonstrated that inoculations with cowpox material provides humans
with immunity from small pox
25. Discovered of vaccination for smallpox. In 1796
Jenner found a young dairymaid, Sarah Nelmes,
who had fresh cowpox lesions on her hand. Using
matter from Sarah’s lesions, he inoculated an
eight-year-old boy, James Phipps, who had never
had smallpox. Phipps became slightly ill over the
course of the next 9 days but was well on the 10th.
On July 1 Jenner inoculated the boy again, this
time with smallpox matter. No disease developed;
protection was complete. In 1798 Jenner, having
added further cases, published privately a slender
book entitled An Inquiry into the Causes and
Effects of the Variolae Vaccinae.
26. Elie Metchnikoff
Father of Innate Immunity
• Elie Metchnikoff discovered that certain cells in the body would
ingest microbes and named them as phagocytes.
27. • Pasteur
showed that some fermentative microorganisms were anaerobic
and others were able to live either aerobically or anaerobically.
Microbial ecology
• Sergei N. Winogradsky (1856-1953) – Soil microbiology –
discovered that soil bacteria could oxidize iron, sulfur and
ammonia to obtain energy and many bacteria incorporate CO2 into
organic matter.
He also isolated anaerobic nitrogen fixing soil bacteria and
studied the decomposition of cellulose.
• Martinus Beijerinck (1851-1931) –
He isolated aerobic nitrogen fixing bacterium Azotobacter,
capable of fixing nitrogen (later renamed as Rhizobium ); and
sulfate reducing bacteria.
Both of them developed enrichment culture technique and
use of selective media, which have been of great importance in
microbiology.
28. VIROLOGY
• Beijerinck characterized viruses as pathogenic molecules that could
take over a host cells mechanisms for their own use.
• Wendell Stanley (1935) – crystallized TMV and crystals consisted of
protein and RNA.
• Knoll and Ruska- Viruses were first observed
with an Electron Microscope in 1939.
29. • Alfred Hershey and Martha Chase (1952) – demonstrated that the
genetic material of some viruses is DNA
• James Watson and Francis Crick (1953) -determined the structure
of DNA
30. Chemotherapy:
There are two types of chemotherapeutic agents: synthetic
drugs and antibiotics.
• Elrlich (1910) introduced an arsenic containing chemical
called Salvarsan to treat Syphilis.
• • Alexander Fleming (1928) – observed that the
mold Penicillium inhibited the growth of bacteria and named
the active ingredient as penicillin. Penicillin has been used
clinically as an antibiotic since the 1940s.
• Domagk and others developed sulfa drugs.
• • Waksman and others developed Streptomycin and other
antibiotics derived from soil organisms.
• • Researchers are tackling the problem of drug-resistant
microbes.
31. • Genetics and Molecular Biology:
• • 1900 – Modern genetics began with the rediscovery of Gregor Mendel's principles of
genetics.
• • Frederick Griffith (1928) - discovered that previously harmless bacteria could change
their nature and become capable of causing disease
• • Avery, McCarty and MacLeod (1940's) – showed that this genetic change was due to
DNA. After this finding came the crucial discovery of the structure of DNA by Watson and
Crick
• • Edward Tatum and George Beadle – studied biochemical mutants of Neurospora to show
how genetic information controls metabolism.
• • Barbara McClintock (1950) – discovered that some genes could move from one location
to another on a chromosome.
• • Early 1960's witnessed a further explosion of discoveries relating to the way DNA controls
protein synthesis.
• • Francois Jacob and Jacques Monod (1961) – discovered mRNA and later made the first
major discoveries about regulation of gene function in bacteria.
• • Microorganisms can now be genetically engineered to manufacture large amounts of
human hormones and other urgently needed medical substances.
• • Late 1960's Paul Berg showed that fragments of human or animal DNA that code for
important proteins can be attached to bacterial DNA. The resulting hybrid was the first
example of recombinant DNA.
32. • Tomorrow's history:
• Microbiology has been in the forefront of research in
medicine and biology and continues to play a role in
Genetic engineering and Gene therapy.
• Genetic engineering – scientists are attempting to
redesign microorganisms for a variety of purposes (drugs,
hormones, vaccines and a variety of biologically important
compounds)
• rDNA technology – enabling us to produce improved
varieties of plants and animals such as pest-resistant
crops and may even enable us to correct genetic defects
in human beings.