Exam 5: Microbial Growth and Control

By controlling the concentration of nutrients added into a chemostat continuously,cells can constantly be maintained at

Counting chambers are used for estimating the number of cells present in a liquid culture.

Which is most abundant and active in divisome complexes?

To determine viable cell counts of a heat-sensitive bacterial isolate,which cell counting method would be best to AVOID?

Which term is most relevant in describing the efficacy of an antimicrobial for use in a clinical setting?

When water activity is low,an organism must

Relative to enzymes in mesophilic microorganisms,which of the following is NOT characteristic of enzymes in psychrophiles?

Defend and explain how FtsZ-type proteins being found in mitochondria and chloroplasts strengthens or weakens the endosymbiosis theory.

An agar plate for counting colonies and maximizing statistical validity should ideally contain

Use the formulas N = N₀2ⁿ and g = t/n. N = final cell number,N₀ = initial cell number, n = number of generations,t = time,g = generation time. Find the generation time if N = 2 × 10⁸,N₀ = 3 × 10⁶ and t = 3 hours.

The number of colonies obtained in a plate count does NOT depend on the

Where would it be best to isolate bacteria from to study the mechanism of the sodium motive force?

Direct microscope counting of stained cells is an accurate method for calculating the exact number of cells in a sample.

Would you expect a xerophilic organism to be halotolerant? Why or why not?

In principle,the chemical composition of membranes in obligate acidophiles could be distinguished from neutrophiles.

The death phase applies to individual cells rather than populations.

One reason food is refrigerated to control microbial growth is because irreversible cell damage is more likely to occur at low rather than high temperatures.

Explain why a hyperthermophile is unlikely to be a human pathogen.

Enumerating the viable and total cell concentration of a population of a microbial isolate can be a really laborious task for a microbiologist.Especially when a microbiologist studies the same isolate for several years,it often becomes practical to determine the relationship between optical density (OD)and cell concentration.Once this relationship (determined by a standard curve)is determined,the OD of an isolate in a broth can be routinely used to determine the population's concentration.Why must a standard curve be prepared for each isolate when using OD measurements to determine cell concentration? Also describe an experiment that would generate this type of standard curve.

Generation of new bacillus-shaped cells starts with one cell elongating and terminates when split into two separate bacilli.