21 Questions
What is the method used for direct cell counts that involves microbial suspension forced through a small orifice?
Electronic counters - Flow Cytometry
Which method is useful for counting bacteria and can distinguish living from dead cells?
Direct Counts on Membrane Filters
What is the unit of measurement for viable cells expressing the population size as colony forming units?
CFU
Which method involves microbial cells being filtered through a special membrane to observe cells against a dark background?
Direct Counts on Membrane Filters
What is the term used to describe the method of plating dilutions of a population on suitable solid medium to calculate the number of cells in the population?
Spread plate and pour plate methods
Which method is easy, inexpensive, quick, but cannot distinguish living from dead cells?
Counting chambers
Which of the following terms describes organisms that require high osmotic pressure for growth?
Halophiles
A bacterial population increases from 10^5 cells to 10^11 cells in 15 hours. What is the generation time (g) of the bacteria?
3 hours
Which phase of the bacterial growth curve is characterized by the bacterial population remaining constant?
Stationary phase
What is the term used to describe bacteria that can survive in harsh conditions but are unable to be cultured using standard laboratory techniques?
Viable but non-culturable
Which of the following organisms is adapted to grow in low pH environments (pH 0-5.5)?
Acidophiles
What is the primary benefit that biofilms provide to the microbial species within the community?
Protection from harsh environmental conditions
What is the average time required for E. coli to replicate its DNA?
40 minutes
Which phase of the growth curve is characterized by a constant rate of growth?
Exponential phase
What is the maximum cell concentration that can be reached by bacteria in a batch culture?
$10^{10}$ cells/mL
Which of the following is NOT a possible reason for entry into the stationary phase?
Increase in cell division rate
Which protein assists RNA polymerase in transcribing genes for starvation proteins during the stationary phase?
RpoS
What is the term used to describe bacteria that are temporarily unable to grow but can resume growth when the environment becomes favorable?
Viable but non-culturable (VBNC) bacteria
What is the term used to describe the irreversible loss of a cell's ability to reproduce?
Loss of viability
Which phase of the growth curve is characterized by a plateau in the total number of viable cells?
Stationary phase
Which of the following is NOT a characteristic of the exponential phase?
Decrease in population size
Learn about the growth curve of microorganisms in batch culture and the replication process of E. coli, including the time it takes for DNA replication and division preparation. Understand the four distinct phases of bacterial growth: Lag, Exponential, Stationary, and Death phase.
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