Growth & Culture of Bacteria
Binary Division
• 1 to 2 to 4 to 8 to ?
Chapter 6
Phases of Growth
• Lag
– Adapt to nutrients
• Log
– Active growth
• Stationary
– Death = Growth rate
• Death
– Nutrients consumed
– pH too low (why?)
• Optimize curves in production
Chapter 6
Log Growth
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Chapter 6
Measuring Growth
• Direct Counts
– Petroff-Hauser Chamber
– Pro’s vs. Con’s
• Serial Dilution
– 10-fold serial dilutions
– Pro’s vs. Con’s
• MPN (Most Probable Number)
– Put 10, 1, and 0.1 ml into 10-mls broth
• Repeat 5 times per volume
– Statistical accurate sampling
– Public Health Standards are written for MPNChapter 6
Chapter 6
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Measuring Growth-cont’d
• Turbidity
– Spectrophotometer
– Scale
• %Transmittance
• Optical Density or Absorbance
• Filtration
– 0.45 - 0.2 um sizes
– Grid Pattern on Filter
– Standards for Public Health
• 0 E.coli / 100 ml of water
– Also used for sterilization
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Chapter 6
Physical Factors: -philes
• pH
– Acido-, Neutro-, Alkaliphiles
– Canned foods-Hot Pack vs. Pressure Cooking
• High Acids- tomatoes
• Neutro-corn, beans, meat
• Temperature
– Psychro-, Meso- Thermophiles
– Growth Curve
– Problems
Chapter 6
Chapter 6
Note the drop-off as you get closer to the Optimum!
Chapter 6
What effect would have a fever have on Mesophiles??
Chapter 6
Temperature Problems
• Thermophiles
– Hot tubs-public
– Heat Resistant Enzymes in PCR
• Psychrophiles
– Cold food (growth in transit)
– Listeria grows in hot dogs
Chapter 6
Salt Concentration
• Halophiles
– Great Salt Lake
– Salt Pork
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Chapter 6
Physical Factors: cont’d
• Moisture
– Beef Jerky
– Lyophilization (Freeze Dry)
• Oxygen
– Aerboes vs. Anaerobes + ------ + ----------
• Osmotic Pressure
– Pseudomonas grows in distilled water
– Jelly- Jams (high sugar)
– Salt Pork (high salt)
Chapter 6
Nutritional Factors
• Carbon Source
– Auto- or Hetero– CO2 or Organic compounds
• Nitrogen Source
– NO3- ==> NO2 ==> NH3 to Amino Acids ==>
Proteins
• Sulfur
• Phosphorus
• Trace Elements
– Fe, some required
– Host Sideophores bind Fe
Chapter 6
More -trophs
• Auxotrophs
– Can live on simple compounds
• NO3-, Glucose
• Make all Amino Acids, Vitamins, etc.
• Prototrophs
– Require complex compounds
• Vitamins, Amino Acids
• Fastidious
• Most Pathogens
Chapter 6
Types of Media
• Complex Medium
– Peptones, Yeast Extract
– Fastidious
– Prototrophs
• Synthetic Medium
– Minimal Media
– Auxotrophs
Chapter 6
Exoenzymes
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•
•
•
Secreted into environment
Catabolize food products
Protease, DNAase, Amylase, Lipase
Used in identification
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Chapter 6
Oxygen Requirments
• Classification
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–
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Aerobic
Anaerobic
Falcultative Anaerobic
Microaerophilic
• Outline for Topic
– Media
– Cultivation
– Oxygen Toxicity
Chapter 6
Flluid Thioglycollate Medium
(FTM)
• Peptones, Yeast Extracts, Glucose
• Thioglycollate-binds O2
• Agar-slow diffusion of O2
• Rezaruin- O2 indicator
Chapter 6
FTM Media
Chapter 6
Growth Chambers
• Candle Jars
– Microaerophillic
– Gas-Paks
– Anaerobes & Faculatative Anaerobes
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Why Anerobes vs. Aerobes
• O2 is reactive-toxic (binds e-’s)
• Requires 4 e-’s to form water
• Intermediates are Free Radicals
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–
–
–
Free Radicals steal e-’s
Oxidization of compounds
Loss of energy from compounds
DNA molecule breaks
Chapter 6
Chapter 6
Chapter 6