Microbial Growth

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Microbial Growth

• Binary Fission
• Growth Rate
• Generation Time
• E. coli can double every 20 minutes
• Many Bacteria have
• 0.5-6 hr Generation Times

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Cell Division

• FTS proteins
• Divisome
• Division septum
• Default shape Coccus
• MRE protein

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Growth Curve

• Batch Culture
• Lag Phase
• Log Phase (Exponential)
• Stationary Phase
• Death Phase
• Cryptic Growth

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Culture Type

• Batch Culture
• Continuous Culture
• Chemostat

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Measuring Bacterial Growth

• Total Cell Counts
• Direct Microscopic Counts
• Petroff-Hauser Counting Chambers
• DAPI
• Flow Cytometer

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Viable Counts

• Plate Counts
• Spread Plate Sample Spread on Solid Agar
  Plates
• CFU colony forming units

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Pour Plate

• Dilute Sample Suspended into Melted Agar

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Dilution
30-300 CFU countable?
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Extinction Dilution

• MPN Most Probable Number

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Turbidity Measurement

• Spectrophotometer

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Controlling Growth

• Temperature
• Minimum
• Optimal
• Maximum

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Temperature Ranges
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Cold Temperatures

• Psychrophile
• Psychrotolerant
• Freezing
• Preserves Bacterial Cultures
• 15 C Optimal
• Maximum 20 C

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Thermophiles

• Thermophile
• Optimal 45 C
• Hyperthermophile
• Optimal 80 C
• Bacteria 95 C
• Archaea 100 C
• Hot Springs

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Other Factors

• pH
• Low pH Used to Preserve Foods
• Acidophiles
• Alkaliphiles
• Buffers Used in Many
• Bacteriological Media
• (Proteins or PO4)

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• Water Availability
• Drying Limits Bacterial Growth
• Halophiles
• Osmophiles
• Xerophiles

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Oxygen

• Aerobe
• Anaerobes
• Obligate vs. Facultative
• Microaerophile

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Growing Anaerobes
Aerotolerant vs. Obligate
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Growth Word List
Growth Curve Lag Phase, Exponential (log) Phase,
Stationary Phase, Death Phase, Cryptic Growth
Measuring Growth Total Cell Counts Direct
Microscopic Counts Petroff-Hausser Counting
Chambers
Bacterial Growth Binary fission Growth
rate Generation Time Exponential Growth Batch
Culture
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Growth Word List 2
Controlling Growth Temperature Minimum, Optimal,
Maximum Psychrophile (psychrotolerant) Mesophile,
Thermophile
Viable Count Plate Counts Spread Plate Pour
Plate Dilution Extinction Dilution
MPN Most Probable Number Turbidity
Measurements Continuous Culture Chemostat
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Growth Word List 3
Halophiles Osmophiles Xerophiles Oxygen Aerobes,
Anaerobes Facultative Microaerophile
Hyperthermophile Freezing pH Acidophile Alkaliphil
e Buffers Water Activity