Transcript Anatomy of Bacteria

Physiology of Bacteria
Bacterial Growth
Bacterial Colony
• “a visible group of bacteria growing on a solid
medium, presumably arising from a single
microorganism”
Requirements for Growth
• Physical: temperature, pH, light, osmotic
pressure, moisture
• Chemical: carbon, nitrogen, sulfur,
phosphorus, trace elements, oxygen
Temperature
• Readings question one:
What are psychrophiles, mesophiles, and
thermophiles?
Psychrophiles
• Desulfofrigus oceanense (Arctic and Antarctic
Oceans)
Mesophiles
E. coli
Thermophiles
Fossilized Microbes from Yellowstone’s Hot Springs
Temperatures
• Minimum: “temperature below which
bacterial growth will not take place”
• Optimum: “temperature at which organisms
grow best”
• Maximum: “temperature above which
bacterial growth will not take place”
• What are the embalming implications
associated with the temperature preference of
bacteria?
pH
• Readings question two:
Describe the pH scale.
Acidophiles: bacteria that are remarkably
tolerant of acidity
Light
• Cyanobacteria: oxygen producing prokaryotes
– thrive in the presence of light
• Yeasts and Molds
– prefer dark areas
• Some bacteria are destroyed by ultraviolet
light.
Osmotic Pressure
• “pressure that develops when two solutions of
different concentrations are separated by a
semi-permeable membrane”
• microorganisms require water for growth and
are made up of 80-90% water
• high osmotic pressure removes necessary
water from a cell
• plasmolysis
• hypertonic solutions
Moisture
• maximum, optimum and minimum
requirement for all microorganisms
• Pathogenic bacteria are usually found in the
body’s tissues
• Fungal diseases are usually found on the body
surface.
Chemical Requirements
• Readings question three:
Describe the differences between autotrophic
bacteria and heterotrophic bacteria.
Heterotrophic Bacteria
• 3 categories:
– 1) strict (obligate) saprophyte
– 2) strict (obligate) parasite
– 3) facultative bacteria:
• Facultative saprophyte: “prefers live organic matter as a
source of nutrition but can adapt to the use of dead
organic matter under certain conditions”
• Facultative parasite: capable of living and growing with
the nutrients that its host provides
Carbon
• one of the most important requirements for
microbial growth
• structural backbone of living matter
• needed for all the organic compounds that
make up a living cell
• ½ of the “dry weight” of a bacterial cell is
carbon
Nitrogen, Sulfur, and Phosphorus
• needed by microorganisms for the synthesis of
cellular material
• e.g. protein, DNA, RNA, ATP
Trace Elements
• iron, copper, and zinc
• essential for the function of certain enzymes
Oxygen
• Microbes that use molecular oxygen (aerobes)
produce more energy from nutrients than
microbes that do not use oxygen (anaerobes)
• Reading question four:
Describe the difference between obligate
aerobes and obligate anaerobes.
Microaerophilic Organisms
• “a microorganism that requires very little free
oxygen”
• only grow in oxygen concentrations that are
lower than those in air
• require about 2 – 10% free oxygen
Facultative Organisms
• Facultative Aerobes: “a microorganism that
prefers an environment devoid of oxygen but
has adapted so that it can live and grow in the
presence of oxygen”
• Facultative Anaerobes: “a microorganism that
prefers an oxygen environment but is capable
of living and growing in its absence”
– E.g. Bacillus anthracis, Corneybacterium
diphtheriae, Escherichia coli
Aerotolerant Organisms
• can grow in the presence or absence of
oxygen
– e.g. Streptococcus pyogenes
Microbial Associations
• normal flora (microbiota)
• transient microbiota
• symbiotic relationship: “organisms live in close
nutritional relationships; required by one or
both members”
– distinguished by the degree to which the host
organism is harmed
Mutualism
• “a symbiotic relationship in which organisms
of two different species live in close
association to the mutual benefit of each”
– e.g. E. coli in the human digestive tract
Commensalism
• “the symbiotic relationship of two organisms
of different species in which one gains some
benefit such as protection or nourishment and
the other is not harmed or benefited”
– e.g. bacteria on skin surface; microorganisms
within the digestive tract
Parasitism
• “an interactive relationship between two
organisms in which one is harmed and the
other benefits”
• many disease-causing bacteria are parasites
• typically the host is macroscopic and the
parasite is microscopic
• roundworms and flatworms are parasites that
are large multi-cellular organisms
• Readings question five:
What is the synergistic effect?
Antagonism
• “mutual opposition or contrary action. The
inhibition of one microorganism by another.”
• Involves competition among microbes
• normal microbiota protect the host against
colonization by potentially pathogenic
microbes
• normal flora produce substances harmful to
the invading microbes (pH, oxygen)