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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. Cell Division. FTS proteins Divisome Division septum Default shape –Coccus MRE protein. Growth Curve. Batch Culture Lag Phase
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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
Cell Division • FTS proteins • Divisome • Division septum • Default shape –Coccus • MRE protein
Growth Curve • Batch Culture • Lag Phase • Log Phase (Exponential) • Stationary Phase • Death Phase • Cryptic Growth
Culture Type • Batch Culture • Continuous Culture • Chemostat
Measuring Bacterial Growth • Total Cell Counts • Direct Microscopic Counts • Petroff-Hauser Counting Chambers • DAPI • Flow Cytometer
Viable Counts • Plate Counts • Spread Plate – Sample Spread on Solid Agar Plates • CFU – colony forming units
Pour Plate • Dilute Sample Suspended into Melted Agar
Dilution 30-300 CFU –countable?
Extinction Dilution • MPN – Most Probable Number
Turbidity Measurement • Spectrophotometer
Controlling Growth • Temperature • Minimum • Optimal • Maximum
Cold Temperatures • Psychrophile • Psychrotolerant • Freezing • Preserves Bacterial Cultures • 15 C Optimal • Maximum 20 C
Thermophiles • Thermophile • Optimal 45 C+ • Hyperthermophile • Optimal 80 C+ • Bacteria 95 C • Archaea 100 C+ • Hot Springs
Other Factors pH Low pH Used to Preserve Foods Acidophiles Alkaliphiles Buffers Used in Many Bacteriological Media (Proteins or PO4)
Water Availability • Drying Limits Bacterial Growth • Halophiles • Osmophiles • Xerophiles
Oxygen • Aerobe • Anaerobes • Obligate vs. Facultative • Microaerophile
Growing Anaerobes Aerotolerant vs. Obligate
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
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
Growth Word List 3 Halophiles Osmophiles Xerophiles Oxygen Aerobes, Anaerobes Facultative Microaerophile Hyperthermophile Freezing pH Acidophile Alkaliphile Buffers Water Activity