Micro 520 Lecture 11

Front 1

What are the differences in nutrient availablities between batch and continuous culture growth?

Back 1

Batch Cultures- conditions remain constant only for a short time during early exponential growth. At later stages when the cell # is high. The composition of the medium will change dramatically

Continuous Growth- cells in constant environment for long periods of time. In the flow system therre is a constant flow of nutrients, they are added to a vessel while spent culture medium is removed at the same rate once at eq the cell # and nutrient status will remain constant and system is in steady state.

Front 2

How can an experimenter vary the cell density in a chemostat experiment while keeping the growth rate constant? Can this type of experiment be done under batch culture growth conditions?

Back 2

At a fixed dilution rate an increase in the nutrient level will result in an increase in the cell density while leaving the growth rate unchanged.

Front 3

Why does the growth rate vary with growth substrate concentration in a manner similar to the enzyme substrate relationship?

Back 3

Ks is the substrate affinity constant (similar to the Km of an enzyme) and is equal to the concentration of growth substrate at which there is half a maximal growth rate, the term Umax is the maxium growth rate

Front 4

What are the four environmental factors that affect microbial growth?

Back 4

1. Temperature
2. pH
3. Water availability
4. Oxygen

Front 5

What molecular events are occuring that affect growth at the 3 cardinal temperatures?

Back 5

1. Minimum- membrane gelling, transport processes so slow that growth cannot occur

2. Optimum- Enzymatic rxns occuring at maximal possible rates (on climb rxns occuring at increasingly rapid rates)

3. Maximum- Protein denaturation, collapse of the CM and thermal lysis

Front 6

Why is there a sharp decrease in growth rate above the optimal growth temperature for most microbes?

Back 6

Protein denaturation collapse of CM, thermal lysis

Front 7

psychrophiles

Back 7

low growth temperature optima

Front 8

mesophiles

Back 8

midrange growth temperature optima

Front 9

thermophile

Back 9

high growth temperature optima

Front 10

hyper thermophile

Back 10

very high growth temp optima