Growth and Cell Division n Growth Not size

Growth and Cell Division n Growth: – Not size, but number of cells n Bacteria: – Binary fission n Yeast: – Budding 1

Cell Division 2

Bacterial Growth Curve n Lag phase n Log phase n Stationary phase n Death phase 3

Measuring Bacterial Concentration Serial dilution/ Standard plate counts n CFU = Colony Forming Unit n CFU/ml n 5

Measuring Bacterial Growth n Direct microscopic counts 8

Measuring Bacterial Growth n Most probable number 9

Measuring Bacterial Growth n Filtration n Turbidity (Spectrophotometry) 12

Physical Factors Affecting Bacterial Growth p. H n Temperature n 14

Physical Factors Affecting Bacterial Growth n Oxygen n Moisture 15

Physical Factors Affecting Bacterial Growth n Osmotic pressure – Salt n Radiation 16

Nutritional Factors Affecting Bacterial Growth n n n n Carbon source Nitrogen source Sulfur/ phosphor Trace elements Vitamins Nutritional complexity Enzymes: – Extracellular – Periplasmic – Cytoplasmic 17

Sporulation n Endospores n Other sporelike bacterial structures 18

Culturing Bacteria — Streak Plates n Streak plate method 19

Culturing Bacteria — Pour Plates n Pour plate method 20

Culture Media Purposes n Selective media n Differential media n Enrichment media 21

Culture Conditions — O 2 n Controlling oxygen content 24

Culture conditions n Maintaining cultures n Preserved cultures n Diagnostic tests n Limitations 25