A%20Tiny%20Bit%20of%20Microbiology

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A Tiny Bit of Microbiology

• EVE 430

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Summary of nutritional groups
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Growth and Reproduction of Bacteria Binary
Fission

• Bacteria basically clone themselves when they
  reproduce
• Binary fission
• The circular DNA molecule is replicated then the
  cell splits into two identical cells, each
  containing an exact copy of the original cell's
  DNA

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Rod-Shaped Bacterium, E. coli, dividing by binary
fission
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Rod-Shaped Bacterium, hemorrhagic E. coli, strain
0157H7 (division)
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Asexual Reproduction by Budding

• Budding yeast
• 1. Cell wall bulges out
• 2 3. Nucleus divides by mitosis
• 4. One nucleus migrates to bud
• 5. Bud cell wall forms and bud breaks off

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Asexual reproduction by budding
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Microbial Population Growth

• Microbial populations grow exponentially when
  supplied with enough nutrients.
• The time it takes to divide is called the
  generation time

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Kinetics of Microbial Population Growth
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End of Log phase is brought about by

• Exhaustion of limiting nutrient
• or
• Build up of toxins (e.g. alcohol in yeast
  cultures)

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For continuous exponential growth

• Continuous culture techniques
• Chemostat

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Factors affecting Microbial Growth

• Temperature
• Substrate Concentration
• pH
• oxygen concentration
• pressure
• In nature competition for nutrients (and space),
  predation and parasitism limit the exponential
  growth of microbes.

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Variations in temperature optima
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Affect of substrate concentration on enzyme
activity (or Microbial growth) The Monod model
qSmax
KS
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Diff microbes have diff pH optima

• Acidophiles acid pH optimal (1 to 5.5)
• Neutrophiles pH 5.5 to 8 optimal
• Alkaliphiles pH 8.5 to 11.5
• Extreme alkaliphiles optimum pH 10 or greater
• Note most bacteria are neutrophiles (Exceptions
  some bact in hot springs have optimum of 1-3)
• Most fungi prefer slight acid (pH 4 to 6)

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Environmental Factors that Influence Microbial
Growth