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
•Microbes can grow at temperatures from < 0°C
(the snow alga, Chlamydomas nivalis) to 110°C
•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
Note the large amount
of material being
precipitated out of the
(about 300C) as it
comes in contact with
ocean water at the sea
Water at atmospheric pressure 1.0 bar 98-100
2.4 bar 125
3.0 bar 134
• 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!
• 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.
•Where are microbes NOT found?
Only inside tissues of
organisms, kept at an area by
Even so, challenges common
(cut finger, get infected transient
Micro-organisms may be classified in the
following large biological groups:
seen to fall
life: Archaea =
• Peptidoglycan cell walls
• Binary fission
• For energy, use organic
• Chitin cell walls
• Use organic chemicals for
• Molds and mushrooms are
multicellular consisting of
masses of mycelia, which are
composed of filaments called
• Yeasts are unicellular
• Absorb or ingest organic
• May be motile via
pseudopods, cilia, or
• Cellulose cell walls
• Use photosynthesis for
• Produce molecular
oxygen and organic
• Consist of DNA or RNA core
• Core is surrounded by a
• Coat may be enclosed in a
• Viruses are replicated only
when they are in a living host
• Multicellular animals
• Parasitic flatworms
and round worms
are called helminths.
• Microscopic stages
in life cycles.
In fact, it is estimated
that we have not yet
isolated more than
1% of all the bacterial
species, and there
are many medically
among them 'as yet
–Various diagnostic test systems
are used to detect specific
bacteria in clinical systems,
–reaction with antibodies in ELISA
–Increasingly PCR-based technology.
• 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.
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.
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
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
PANDEMIC ( a widespread epidemic
distributed or occuring widely throughout a
region, country, continent, or globally
Organism Time needed to
consume body weight
Human 180 Days
Pig 20 Days
Yeast 30 Minutes
Lactobacillus 10 Minutes
Micrococcus 3 Minutes
• 1. The invisible world of microbes underlies and
shapes what we call the "visible world".
• 2. Microbes have extraordinary genetic and
• 3. Microbial metabolism can create anaerobic
environments, and anaerobic microbes can use
• 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
MICROBES & ECOLOGY
• Many microbes (bacteria and fungi) are
decompsers (saprotrophic) and break down
• Decomposers release nutrients form dead
organisms and return them to the
• These free nutrients are recycled & used by
other organism for growth, repair, &
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.
• Microbes are widely used in food
• Examples of microbial food products are:
• Cheese, sour cream, yogurt, butter milk,
vinegar, bread and soy sauce.
• Typically involves bacteria and/or yeast.
• One of major human problems: getting
rid of microbes, or preventing their
• Practical problem for food, beverage,
cosmetic, pharmaceuticals, other
Disease can come about in several overlapping
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
Disease can come about in several overlapping
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
The majority of microbes
persist attached to
surfaces within a
ecosystem and not as
free floating organisms.
Microbiol. Mol. Biol. Rev. 64:847-867 (2000)
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