Download Bacteria and Environmental Conditions

Bacteria and
Environmental
Conditions
Patricia Sidelsky
Microbiology
156- Class 10
Energy for the Cell
The energy currency of the cell is ATP
 ATP is adenosine tri phosphate
 Adenosine tri phosphate is used by the cell
for the completion of all cellular process that
have energy requirements
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Oxygen
Aerobic bacteria – Do oxidative
phosphorylation( production of ATP)
 Tolerate oxygen in the environment
 Have mechanisms for tolerating an oxygen
rich environment

Energy pathways- with oxygen
Sugars and other molecules are broken down
into intermediate molecules
 Glucose may be broken down into pyruvic acid
 2C fragment from pyruvic acid( Acetyl COA)
is fed into Kreb’s Cycle and Electron
transport chain to produce ATP

Anaerobic pathways
Use alternate sources of electrons and
hydrogen
 Oxygen is a poison
 No tolerance of oxygen in the environment
 Break down sugars into smaller carbon
fragments and generally carry out a type of
fermentation
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Terminology
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Aerobe – An organism that can grow in oxygen
Obligate aerobe- An organism that requires oxygen as
the terminal electron acceptor in the electron
transport chain
Anaerobe – Cannot grow in the presence of oxygen
Aerotolerant – Like Enterococcus – oxygen is not a
factor in the growth of these organiss
Capnophile – Likes high levels of carbon dioxide
Facultative anaerobe – Do not require oxygen but
grow better in its presence
Microaerophile – prefers levels of oxygen below 10%
Free radicals
Aerobic bacteria make free radicals during
aerobic respiration
 Free radicals can be damaging to the cell
 The aerobic bacteria have the capacity to
break down the free radicals
 Obligate aerobes make catalase or superoxide
dismutase that breaks down free radicals

Halophiles
Grow in the presence of NaCl or other salts
at levels greater than 0.2M
 These organisms have adjusted their
membranes and metabolism to a hypertonic
environment
 Their proteins and biochemistry have also
adapted to this environment
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Halotolerant
These orgnisms can tolerate lower levels of
salt
 They are osmotolerant and can adapt to a
varying level of salt in their environment by
accumulating potassium inside of their cells

pH
pH is a measure of the hydrogen ion activity
of a solution
 The pH scale extends from 0-14
 0-7 is the acidic side of the scale
 7-14 is the basic side of the scale
 7 is neutral
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Acidophiles
Prefer an environment of 0-5.5
 The lower the number the more acidic the pH

Neutrophiles
Have a pH preference for levels between 5.5
and 8
 Many pathogens fall in this group
 Bacteria that can adapt to varying levels of
pH are many of the enteric pathogens
 E. coli and Salmonella have adapt by altering
the proton pumps and other mechanisms for
the movement of ions and molecules across
their membrane

Waste products
Some bacteria give off waste by products
that alter the environment and therefore
adjust their environment
 Fermentative microbes produce acids which in
fact change their environment in the small
intestine and large intestine
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Alkalophiles
Alkalophiles prefer environments with high
pH.
 This environment is basic or alkaline
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Temperature preferences( cold)
Psychrophiles – Live on the ice in Anarctica
 These organisms can survive extreme
conditions and even grow in the cold
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Psychrotrophs – Live and grow in the
refrigerator.
 These organisms can grow at temperatures of
7oC, but optimally can grow at temperature up
to 30oC
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Mesophiles
Prefer temperatures 25-40oC
 Human pathogens are mesophiles because
human body temperatures fall within this
range

Thermophiles
These organisms can grow at temperatures
higher than 55oC
 The may be found in compost heaps or piles of
hay
 They may also be found in hot water lines
 Their proteins have more stable structures at
higher temperature
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Hyperthermophiles
These microbes can survive in boiling water
 They can be found in the geysers of
Yellowstone Part
 They tolerate these high temperatures
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New Work - Table
Plate bacteria on different pH
concentrations, acidic, neutral, and alkaline.
Place in the holder
 Plate bacteria. Place in incubators at varying
temperature levels
 Plate bacteria. Place one set in incubator(
oxygen)
 Plate bacteria. Place the set in the anaerobic
container and incubate.
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