Growth & Culture of Bacteria

Chapter 6

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

Chapter 6

Chapter 6

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 MPN

Chapter 6

Chapter 6

Chapter 6

Chapter 6

Chapter 6

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

Chapter 6

Chapter 6

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

Chapter 6

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

• Secreted into environment

• Catabolize food products

• Protease, DNAase, Amylase, Lipase

• Used in identification

Chapter 6

Chapter 6

Oxygen Requirments

• Classification– 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

Chapter 6

Chapter 6

Why Anerobes vs. Aerobes• O2 is reactive-toxic (binds e-’s)

• Requires 4 e-’s to form water

• Intermediates are Free Radicals– Free Radicals steal e-’s– Oxidization of compounds– Loss of energy from compounds– DNA molecule breaks

Chapter 6

Chapter 6