Lecture 5
? 5.1 Microbial Nutrition
? 5.2 Culture Media
? 5.3 Laboratory Culture of Microorganisms
? 6.1 Cell Growth and Binary Fission
? 6.2 Peptidoglycan Synthesis and Cell Division
? 6.3 Population Growth
? 6.4 The Growth Cycle
? 6.5 Direct Measurements of Microbial Growth
? 6.6 Indirect Measurements of Microbial
Growth
Overview of Cell Metabolism
Energy Classes of
Microorganisms
? phototrophs,light as energy source
? chemotrophs,chemicals as energy
source
– chemoorganotrophs,organic chemicals
– chemolithotrophs,inorganic chemicals
Culture Media
? Defined - made from purified chemicals
? Complex - exact chemical composition
not known
Liquid Solid
Some bacteria
can complete
one generation
in as little as 20
min,
Binary Fission
Bactoprenol
Population Growth
? Growth rate = change in cell # / time
? Generation time (g) = time for formation
of two cells from one = doubling time
? If generation time remains constant,then
exponential growth
Rate of Growth in Culture
Doubling Time
= 30 min
Exponential
Growth
Calculation of Generation Time
Slope = log 2 / g = 0.301/g
Stationary Phase
? A single cell with generation time of 20 min
?a population after 48 h that would weigh
4000 times the weight of the earth.
? Growth is limited by the lack of an essential
nutrient or the production of inhibitory
waste product
Direct Microscopic Count
Petroff-Hauser
counting chamber
Requires at least
106 cells/ml
Counts all cells; cannot distinguish between living and dead
Viable Count
CFU = colony forming unit
Serial Dilutions
Turbidity Measurements