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

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

Measuring Growth-cont’d Turbidity –Spectrophotometer –Scale %Transmittance Optical Density or Absorbance Filtration – um sizes –Grid Pattern on Filter –Standards for Public Health 0 E.coli / 100 ml of water –Also used for sterilization

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

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

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- –CO 2 or Organic compounds Nitrogen Source –NO 3 - ==> NO 2 ==> NH 3 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 NO 3 -, 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

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 O 2 Agar-slow diffusion of O 2 Rezaruin- O 2 indicator

Chapter 6 FTM Media

Chapter 6 Growth Chambers Candle Jars –Microaerophillic –Gas-Paks –Anaerobes & Faculatative Anaerobes

Chapter 6

Why Anerobes vs. Aerobes O 2 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