MICROBIOLOGY LECTURE
SERIES
YEAR 2: BACHELOR OF VETERINARY
MEDICINE
BY
DR MAHACLA OMUNG’ALA ODONGO
© 2016
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MICROBIOLOGY LECTURE TOPICS
Introduction and History of Microbiology
Survey and Classification of Microorganisms
Microscopy and Staining
Bacterial Ultrastructure (Anatomy) and Function
Growth, Reproduction and Nutrition of Bacteria
Cultivation of Bacteria in the Laboratory
Bacterial Metabolism and Biochemical Tests
Bacterial Genetics and Recombinant DNA
Technology/Genetic Engineering of Bacteria
 Control of Microorganisms
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Introduction
Definition of Microbiology
 A specialized branch of Biology that studies
living organisms ordinarily too small to be seen
without the help of special magnifying
instruments called microscopes.
 Organisms
studied
in
Microbiology
generally referred to as Microorganisms.
are
 Therefore Microbiology is the study of
Microorganisms, which include bacteria, etc.
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Introduction - Microorganisms
Microorganisms
Cellular organisms
• Bacteria
• Archaebacteria
• Fungi
• Algae
• Protozoa
• Helminthes
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Acellular organisms
• Viruses
• Viroids
• Virusoids
• Prions
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Introduction – Disciplines of Microbiology

Medical Microbiology- Studies disease-causing (pathogenic)
microorganisms.

Immunology- Studies body defense system (immune system)
against pathogens and other foreign substances.

Food Microbiology- Studies microorganisms responsible for
food spoilage.

Industrial Microbiology- Studies microorganisms used in various
industries to enhance the production of useful industrial
products such as pharmaceuticals, vitamins, organic acids,
alcohols, solvents, methane, and enzymes.
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Introduction – Disciplines of Microbiology

Environmental Microbiology- Studies microorganisms that play a
useful or harmful role in the various ecosystems such as soil
and water.

Agricultural Microbiology- Studies microorganisms associated with
crops in terms of diseases and beneficial effects such as
nitrogen fixation.

Recombinant DNA Technology/Genetic Engineering- Involves
techniques used to deliberately alter the genotypes of
microorganisms for the purposes of mass production of useful
products such as hormones, vaccines, drugs, enzymes, or for
generating GMOs with unique biosynthetic abilities. This is the
most powerful and rapidly growing area of modern
microbiology.
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Introduction – Why we study microorganisms
 To understand how they cause diseases in humans and
animals, i.e. to understand their pathogenicity
mechanisms.
 To design or formulate their control measures.
 To exploit their useful attributes/properties in areas such
as disease diagnosis, epidemiology, dairy industry,
antibiotic treatment, and vaccine production.
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Introduction – Importance of microorganisms
1.
Microorganisms cause many infectious diseases in humans,
animals, and plants; some microorganisms cause food
spoilage.
2.
Some
microorganisms
(normal
flora
or
indigenous
microorganisms) found in certain sites of the body are
beneficial to humans and animals, e.g. normal flora protect
humans and animals against pathogenic microorganisms,
provides vitamins such as B12, and for ruminant livestock,
they enable them to digest plant fiber.
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Introduction – importance of microorganisms
3.
Microorganisms immensely contribute to the sustenance of
human and animal life on Earth in the following ways:

Cyanobacteria and algae in the oceans are a major sink
of CO2, a greenhouse gas.

Microbes release nutrients from dead organisms,
making them available to the rest of the ecosystem,
i.e. they are the key agents in the recycling of
nutrients such as carbon, sulfur, phosphorus and
nitrogen.

Nitrogen fixing bacteria in association with roots of
leguminous plants act as biofertilizers when they fix
atmospheric nitrogen into ammonia which is then
utilized by plants.
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Introduction – importance of microorganisms
4.
Some microbes convert organic wastes into useful energy,
e.g. biogas, and solvents such as alcohol, acetone and
butanol; some rid the environment of toxic chemicals.
5.
Because of their short generation times (e.g. 20 minutes for
E. coli), microbes are useful tools for the study of genetic,
metabolic, and other chemical processes in higher organisms.
6.
Microbes are some of the key tools in recombinant DNA
technology whose applications can be found in medicine,
industry and agriculture.
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History of Microbiology
 Started with man’s quest to know the causes
of diseases
 The four early theories for disease causation
were:
1.
2.
3.
4.
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Theurgical theory- basis was biblical (i.e. diseases due to divine
wrath or supernatural powers)
Miasmatic theory- advanced by Hippocrates (diseases due to solar
influences, e.g. stars)
Pore theory- based on body form (e.g. good symmetrical body, good
health, bad symmetry, bad health).
Theory of Spontaneous Generation (Abiogenesis)-life arose
spontaneously.
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History- theory of Spontaneous generation
 Ist discounted by Francesco Redi in 1665 (1626-1697) with
his meat and maggot experiment.
 Abbe Lazaro Spalanzani (1729-1799) was the 2nd person to
discount this theory with his boiled beef broth
experiment.
 H. Schroeder and T. von Dusch in 1850 also opposed this
theory with their cotton-filtered heated broths
experiment.
 Louis Pasteur (1822-1895) in 1864 finally burried this
thoery with his long narrow goose-necked flasks with
heated nutrient solutions experiment.
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History of modern microbiology
 Modern Microbiology is said to have began in 1664 when
Robert Hooke devised a compound microscope and used it
to observe fleas, sponges, bird feathers, plants and
molds, among other items.
 In 1676, a Dutch fabric merchant called Antony van
Leeuwenhook (1632-1723) devised a crude microscope
from ground glass and used it to observe tiny organisms
or “wee animacules” as he called them. He was able to
observe, describe and draw the various microbial forms
including bacteria in pond water with accuracy. For this
discovery, he is thus recognized as the “Father of
Microbiology”. Leeuwenhook’s microscope could only
magnify microbes 200 times.
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History- contd;
In 1711 Joblot established that microbes were present in
air.
 In the 18th century, the Germ theory was advanced by
Fracastoro and supported by Plenciz (1762). This theory
stated that “living things cause disease and that
different germs were responsible for different diseases”.
 In the 19th Century the following developments took
place in the field of Microbiology:
1. Appert invented canning as a method of food preservation hence the
name appertization.
2. Schwann came up with heating as a method of preventing
contamination of infusions.
3. Schroda and van Dusch invented cotton wool as an air sterilizing
medium and also established the presence of thermophilic and
mesophilic bacteria.
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History- more developmemts of the 19 th century
 Ignaz Philipp Semmenlweis (1818-1865) a Hungarian physician,
showed that child bed fever was spread by physicians and could be
prevented by careful handwashing with chloride and lime
(antiseptics).
 In 1856, Louis Pasteur devised pasteurization as a method of
removing unwanted microbes from wine.
 John Tyndall (1820-1893), an English physicist developed the process
of intermittent heating (Tyndallization) as a method of killing sporeforming bacteria.
 In 1865, Joseph Lister (1827-1912), an English surgeon introduced the
use of carbolic acid (Phenol, the active ingredient in Listerine) as
antiseptic spray during surgery, a move that greatly reduced the
incidence of post surgical infections; for this he is recognized as the
“Father of Antiseptic Surgery”.
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History- more developmemts of the 19th century
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Martinus Beijerinckii (1851-1931) formulated the
“Enrichment culture technique” for microorganisms.
In 1874, Hansen described Mycobacterium leprae.
In 1879, Neisser discovered Neisseria gonorrhoea
In 1880, Alexander Ongston described Stahylococci in
abscesses and suppurative lesions.
In 1880, Eberth observed Salmonella typhi.
In 1883, Loeffler observed and described
Corynebacterium diphtheriae.
In 1884, Hans Christian Gram developed the Gram
staining technique.
In 1886, Rosenbach described Clostridium tetani.
In 1887, Weichselbaum isolated and described
Neisseria meningitidis; Bruce identified Brucella
melitensis.
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History- more developmemts of the 19th century
 Robert Koch (1843-1910) a German physician
made the following discoveries:
1.
He discovered Bacillus anthracis in 1876.
2.
In 1881, he invented agar as a solidifying agent for bacteriological
culture media.
3.
In 1882, he discovered Mycobacterium tuberculosis.
4.
In 1883, he discovered Vibrio cholerae.
5.
In 1884, he developed ‘Koch’s Postulates”, as criteria for linking the
microbial isolate to disease.
NB: These have since been replaced by “Molecular Postulates”.
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History- developments of the 19th and 20th centuries
 In 1892 Dmitri Iwanowski (1864-1920), a Russian plant
scientist discovered tobacco mosaic virus, then
referred to as a filtrable agent.
 In 1898 Loeffler and Frosch discovered the foot-andmouth disease virus.
 In 1902, Walter Reed discovered Yellow fever virus.
 In 1911, Peyton Rous isolated the Rous sarcoma virus
from fowls.
 In the 1930s Goodpasture developed the technique of
growing viruses in chick embryos.
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History- The Era of Immunization
 In 1796 Edward Jenner, an English physician discovered the
small pox vaccine.
 In 1881, Louis Pasteur discovered Anthrax vaccine.
 In 1885, Louis Pasteur discovred Rabies vaccine.
 In 1888, Nuttal discovered humoral immunity.
 In 1889, Buchner discovered complement.
 In 1980, Emil von Behring and Kitasato discovered the
antibody.
 In 1893, Elie Metchnikoff discovered phagocytes and the
process of phagocytosis and hence CMI.
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History- The Era of Chemotherapy
 In 1909, Paul Erhlich discovered neosalvarsan, a
treponemacidal drug for the treatment of syphilis. He
is recognized as the “Father of Chemothrapy”.
 Gerhardt
Domagk
(1895-1964)
discovered
the
antibacterial effect of prontosil, an azo dye derived
from para-aminobenzene sulphonamide.
 In 1928, Alexander Fleming (1881-1955) discovered the
antibiotic penicillin.
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History- The Era of Molecular Biology
(1928-2008)
 In 1928 Frederick Griffith discovered the process of natural
transformation among bacteria.
 In 1944 Oswald T Avery, Colin MacLeod and Maclyn McCarty
demonstrated that DNA was indeed the hereditary
(genetic) material.
 In 1946 Lederberg and Tatum discovered the process of
gene transfer called conjugation.
 In 1948 Barbra McClintock discovered transposable genetic
elements in maize; 2 years later they were discovered in
bacteria.
 In 1952 Joshua Lederberg and Norton Zinder discovered the
process of gene transfer in bacteria called transduction.
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History- The Era of Molecular Biology
(1928-2008)
 In 1953 James Watson, Francis Crick, Rosalind Franklin, and
Maurice Wilkins determined the structure of DNA.
 In 1959 Rodney Porter determined the structure of
immunoglobulin.
 In 1966 Marshall Nirenberg and H. Gobind Khorana discovered
the genetic code.
 In 1970 Hamilton Smith reported the discovery of the first
restriction enzyme.
 In 1973 Herbert Boyer and Stanley Cohen were the first to
clone DNA using plasmids.
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History- The Era of Molecular Biology
(1928-2008)
 In 1975 Cesar Milstein, Georges Kohler, and Niels Kai Jerne
developed the technique for making monoclonal
antibodies.
 In 1977 Fred Sanger, Steven Niklen and Alan Coulson developed
methods for sequencing DNA.
 In 1982 Stanley Prusiner isolated the infectious protein
called prion.
 In 1983 Luc Montagnier discovered HIV as the cause of
AIDS.
 In 1985 Karry Mullis invented the polymerase chain
reaction (PCR).
 1997 the first complete nucleotide sequence of all the
chromosomes of a eukaryote (yeast) is reported.
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