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

Temperature Ranges

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 AnaerobesAerotolerant vs. Obligate

Growth Word List

Bacterial Growth

Binary fission

Growth rate

Generation Time

Exponential Growth

Batch Culture

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

Growth Word List 2

Viable Count

Plate Counts

Spread Plate

Pour Plate

Dilution

Extinction Dilution

MPN – Most Probable Number

Turbidity Measurements

Continuous Culture

Chemostat

Controlling Growth

Temperature

Minimum, Optimal, Maximum

Psychrophile (psychrotolerant)

Mesophile, Thermophile

Growth Word List 3

Hyperthermophile

Freezing

pH

Acidophile

Alkaliphile

Buffers

Water Activity

Halophiles

Osmophiles

Xerophiles

Oxygen

Aerobes, Anaerobes

Facultative

Microaerophile