1. rstobgi@gmail.com

2. rstobgi@gmail.com
Microorganisms are the most
abundant organisms on earth,
found everywhere; air, water,
soil, rocks (live bacteria even
found in rocks more than a mile
below earth's surface)
Billionsper gram of fertile soil

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•Microbes can grow at temperatures from < 0°C
(the snow alga, Chlamydomas nivalis) to 110°C
(Pyrolobus fumarii).
•A microbe that can grow in water over 100°C.
• The P. fumarii grows under the sea at
hydrothermal vents where the water pressure is
very high.

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Note the large amount
of material being
precipitated out of the
super-heated water
(about 300C) as it
comes in contact with
ocean water at the sea
floor (4C).

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Steam (C)
Water at atmospheric pressure 1.0 bar 98-100
2.4 bar 125
3.0 bar 134

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• Most of the organisms we will examine
will grow at 20-50°C.
• Microbes are also present in saturated
salt lakes, in acid mine drainage that is
below pH 1,
• In environments devoid of oxygen, in
soil, and on you!

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• Micro-organisms are microscopic in size.
• The smallest body that can be seen with the
naked eye is about 100 μm.
• All medically related bacteria are smaller than this
and a microscope is therefore necessary
• When spread on solid media, bacteria (and fungi)
form macroscopically visible structures contain at
least 108 cells, known as colonies.

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•Where are microbes NOT found?
Only inside tissues of
organisms, kept at an area by
defensive mechanisms.
Even so, challenges common
(cut finger, get infected transient
bacteraemia).

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Micro-organisms may be classified in the
following large biological groups:
Classification

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• theBacteria,
• theArchaea
• theEukarya.
All living
forms are
seen to fall
within
three
domains of
life: Archaea =

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• Prokaryotes
• Peptidoglycan cell walls
• Binary fission
• For energy, use organic
chemicals, inorganic
chemicals, or
photosynthesis

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• Prokaryotic
• Lack peptidoglycan
• Live in extreme
environments
Include:
– Methanogens
– Extreme halophiles
– Extreme thermophiles

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• Eukaryotes
• Chitin cell walls
• Use organic chemicals for
energy
• Molds and mushrooms are
multicellular consisting of
masses of mycelia, which are
composed of filaments called
hyphae
• Yeasts are unicellular

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• Eukaryotes
• Absorb or ingest organic
chemicals
• May be motile via
pseudopods, cilia, or
flagella
Trypanosoma
Giardia

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• Eukaryotes
• Cellulose cell walls
• Use photosynthesis for
energy
• Produce molecular
oxygen and organic
compounds
Diatoms

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• Acellular
• Consist of DNA or RNA core
• Core is surrounded by a
protein coat
• Coat may be enclosed in a
lipid envelope
• Viruses are replicated only
when they are in a living host
cell

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• Eukaryote
• Multicellular animals
• Parasitic flatworms
and round worms
are called helminths.
• Microscopic stages
in life cycles.

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Microbial characteristics

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In fact, it is estimated
that we have not yet
isolated more than
1% of all the bacterial
species, and there
are many medically
important organisms
among them 'as yet
uncultivated' micro-
organisms.

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–Various diagnostic test systems
are used to detect specific
bacteria in clinical systems,
including,
–reaction with antibodies in ELISA
formats,
–immunofluorescence and
–Increasingly PCR-based technology.

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• Typing of bacterial isolates is
necessary for epidemiological
investigations in outbreaks and for
surveillance, and a variety of
phenotypic and genetic methods has
evolved for the identification of strains.

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Bacteria 538
Fungi 317
worms 287
Viruses 208
Parasites 57

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archea
Eubacteria
Protozoan
with alteration
AnO2 O2

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Bacteria and Archaea are present in all
environments that support life. Procaryotes
have the usual nutritional requirements for
growth of cells, but many of the ways that
they utilize and transform their nutrients are
unique. This bears directly on their habitat
and their ecology.

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Early Earth was AnO2, Cyanobacteria
build up of O2 in atmosphere from 0% to
20% around 2 billion years ago (BYA).
Lithotrophic and fermentative modes of
metabolism were the first to develop in
early prokaryotes.

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2O2
- + 2H+ SOD H2O2+O2
2H2O2
Catalase 2H2O +O2
SOD=Superoxide dismutase

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Neutrophiles （ 5 to 8）
Acidophiles （below 5.5）
Alkaliophiles （above 8.5）

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ENDEMIC ( disease present or
usually prevalent in a population or
geographic area at all times
EPIDEMIC ( disease occuring suddenly
in numbers clearly in access of normal
expectancy
PANDEMIC ( a widespread epidemic
distributed or occuring widely throughout a
region, country, continent, or globally

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Organism Time needed to
consume body weight
Human 180 Days
Pig 20 Days
Yeast 30 Minutes
Lactobacillus 10 Minutes
Micrococcus 3 Minutes

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• 1. The invisible world of microbes underlies and
shapes what we call the "visible world".
• 2. Microbes have extraordinary genetic and
metabolic diversity.
• 3. Microbial metabolism can create anaerobic
environments, and anaerobic microbes can use
these environments.
• 4. Different microbes are adapted to survive and
use an enormous range of environments, both
inanimate and animate.
• 5. Among all life forms on earth, microbes have
the widest range of genetic and evolutionary
diversity.

32. MICROBES & ECOLOGY
• Many microbes (bacteria and fungi) are
decompsers (saprotrophic) and break down
organic matter.
• Decomposers release nutrients form dead
organisms and return them to the
ecosystem.
• These free nutrients are recycled & used by
other organism for growth, repair, &
continuation.

33. MICROBES & INDUSTRY
• Microbes are used in many industrial
products and processes.
• Some examples are the development of
medicines (e.g. antibiotics), the
production of chemicals (alcohols,
organic acids, acetone), the production
of various enzymes, vitamins, hormones,
steroids, and perfumes.

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• Microbes are widely used in food
production.
• Examples of microbial food products are:
• Cheese, sour cream, yogurt, butter milk,
vinegar, bread and soy sauce.
• Typically involves bacteria and/or yeast.

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• One of major human problems: getting
rid of microbes, or preventing their
growth.
• Practical problem for food, beverage,
cosmetic, pharmaceuticals, other
industries.

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Disease can come about in several overlapping
ways
1. Some bacteria are entirely adapted to the
pathogenic way of life in humans. They are never
part of the normal flora but may cause subclinical
infection, e.g. M . tuberculosis
2. Some bacteria which are part of the normal flora
acquire extra virulence factors making them
pathogenic, e.g. E. coli

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Disease can come about in several overlapping
ways
3. Some bacteria which are part of the normal flora
can cause disease if they gain access to deep
tissues by trauma, surgery, e.g. S. epidermidis
4. In immunocompromised patients many free-living
bacteria and components of the normal flora can
cause disease, especially if introduced into deep
tissues, e.g. Acinetobacter

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Growth/Culture condition
The majority of microbes
persist attached to
surfaces within a
structured biofilm
ecosystem and not as
free floating organisms.
Microbiol. Mol. Biol. Rev. 64:847-867 (2000)