Microbiology Chapter 5
Most organisms can tolerate a temperature range of about
25-40°C.
An agar plate for counting colonies and maximizing statistical validity should ideally contain
30 to 300 colonies.
Serial dilutions are generally made
All of the above apply.
When counting colonies on an agar plate,
All of the above apply.
Which of these statements is/are TRUE?
All of the above are true.
What makes penicillin a powerful antibiotic?
Both A) and B) are correct.
Cold environments are usually sterile.
False
Direct microscope counting of cells is an easy and accurate method of computing the exact number of cells in a sample.
False
Irreversible cell damage is more likely to occur at low rather than high temperatures.
False
Organisms generally respond equally to a given environmental factor.
False
Organisms living in boiling springs must be rapid growers with fast doubling times.
False
The death phase applies to individual cells rather than populations.
False
The lag phase does NOT occur if all the cells in the culture are viable.
False
The optimal growth pH represents the pH of the intracellular environment.
False
The optimum temperature is usually closer to the minimum temperature than the maximum temperature.
False
Turbidity measurements are rapid but are not particularly accurate.
False
With a few minor exceptions, the time required for a bacterial growth cycle is generally the same, regardless of the bacterial species.
False
Proteins involved in prokaryotic cell division are
Fts proteins.
Formation of the divisome begins with the attachment of which protein in a ring around the center of the cell?
FtsZ
What is the function of bactoprenol?
It is a hydrophobic alcohol that transports peptidoglycan precursors across the cytoplasmic membrane.
The major shape-determining protein among prokaryotes is
MreB.
Consider solution A (pH 6) and solution B (pH 9). Which of the following statements is CORRECT?
Solution B is 1,000 times more alkaline (basic) than solution A.
A growth curve can typically be plotted by monitoring a microbial population in a batch culture.
True
An alkaliphile would likely be found in soda lakes and high carbonate soils.
True
An increase in microbial density is synonymous with growth.
True
Based on studies with obligate acidophiles, high concentrations of hydrogen ions are required for membrane stability.
True
Counting chambers are used for estimating the number of cells present in a liquid culture.
True
Factors affecting an organism's minimal growth temperature are not entirely understood.
True
For most purposes, viable counting usually gives accurate information about the number of active cells present in a culture volume.
True
In a chemostat, growth rate and growth yield can be controlled independently.
True
In a chemostat, the doubling rate and population density can be controlled independently.
True
In the stationary phase, there is no net increase or decrease in cell number.
True
Knowledge of microbial growth patterns is useful in working with the control of microbial growth.
True
Many obligate anaerobes are killed by oxygen.
True
One problem with batch cultures is the change in the chemical composition of the medium as growth progresses.
True
Planktonic cells remain in suspension, while sessile cells adhere to a surface.
True
Some microbes can grow in boiling water.
True
Taq polymerase was isolated from a thermophile and is used in the polymerase chain reaction (PCR) technique.
True
The main reactions of cell synthesis are the polymerization reactions that make macromolecules from monomers.
True
The rates of exponential growth (in the exponential phase) vary greatly.
True
Superoxide dismutase is indispensable to
aerobes.
An organism capable of growth at full oxygen tensions of 21% is
aerobic.
Which environmental factor(s) influences microbial growth?
all of the above
Which of the following forms of oxygen is/are generally toxic to living organisms?
all of the above
In which type of culture(s) does one find a closed system?
batch culture
The process by which two cells arise from one is known as
binary fission.
Population growth is measured by
changes in the number of cells and in the cell mass.
For most physiological experiments, it is desirable for cells to be in the
exponential phase.
When the population doubles during a constant time interval, the growth is said to be
exponential.
As a group, which organisms tend to be most acid-tolerant?
fungi
The time interval required for the formation of two cells from one is called the
generation time.
When water activity is low, an organism must
increase its internal solute concentration.
The time between inoculation and the beginning of growth is usually called the
lag phase.
The cardinal temperatures are the
minimum, optimum, and maximum temperatures taken together.
Divisomes are responsible for
none of these.
Organisms able to live in environments with high sugar concentrations are
osmophiles.
Superoxide dismutase and catalase work together to convert superoxide back to
oxygen.
A microbe growing in a refrigerator is likely a
psychrophile.
The cytoplasmic membrane must be in a(n) ________ state for proper functioning.
semi-fluid
The partition that is a result of the inward growth of the cytoplasmic membrane and cell wall from opposing directions is known as the
septum.
The number of colonies obtained in a plate count does NOT depend on the
size of the colonies.
In general, compared with most prokaryotic microorganisms, most eukaryotic microorganisms grow
slower.
Cell density in a chemostat is controlled by
the concentration of the limiting nutrient.
Cryptic growth occurs when
the number of cells being generated equals the number of cells dying.
Growth is defined as an increase in
the number of cells.
Oxygen in its normal ground state is referred to as
triplet oxygen.
The ratio of the vapor pressure of the air in equilibrium with a substance to the vapor pressure of pure water is known as
water activity.
Under what conditions would a lag phase NOT occur?
when an exponentially growing culture is transferred into fresh medium
