1

Growth and Cell Division

Growth:– Not size,

but number of cells

Bacteria:– Binary

fission Yeast:

– Budding

2

Cell Division

3

Bacterial Growth Curve

Lag phase

Log phase

Stationary phase

Death phase

5

Measuring Bacterial Concentration

Serial dilution/ Standard plate counts

CFU = Colony Forming Unit

CFU/ml

8

Measuring Bacterial Growth

Direct microscopic counts

9

Measuring Bacterial Growth Most probable

number

12

Measuring Bacterial Growth

Filtration

Turbidity (Spectrophotometry)

14

Physical Factors Affecting Bacterial Growth

pH Temperature

15

Oxygen

Moisture

Physical Factors Affecting Bacterial Growth

16

Osmotic pressure– Salt

Radiation

Physical Factors Affecting Bacterial Growth

17

Nutritional Factors Affecting Bacterial Growth

Carbon source Nitrogen source Sulfur/ phosphor Trace elements Vitamins Nutritional complexity Enzymes:

– Extracellular– Periplasmic– Cytoplasmic

18

Sporulation

Endospores

Other sporelike bacterial structures

19

Culturing Bacteria — Streak Plates Streak plate method

20

Culturing Bacteria — Pour Plates Pour plate method

21

Culture Media Purposes

Selective media

Differential media

Enrichment media

24

Culture Conditions — O2

Controlling oxygen content

25

Culture conditions

Maintaining cultures

Preserved cultures

Diagnostic tests

Limitations