Bacteria and Environmental Conditions

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Bacteria and Environmental Conditions

• Patricia Sidelsky
• Microbiology
• 156- Class 10

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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

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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 Krebs Cycle and Electron transport chain to
  produce ATP

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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

• 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

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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

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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

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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

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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

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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
• 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

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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.