A medium that contains yeast extract, glucose, and peptones would be a(n)
complex medium
A bacterial suspension produces a turbidity reading that corresponds to 5 x 107 CFU/ml. A viable plate count of the same suspension produces a concentration of only 1 x 105 CFU/ml. You most correctly conclude that
Turbidity is an accurate measure of concentration, but is measures both live and dead cells.
In metabolism, ______ reactions liberate energy used to make ATP, whereas ______ reactions require energy supplied by the hydrolysis of ATP.
catabolic, anabolic
The ATP made by oxidative phosphorylation
is powered by chemiosmosis using a proton gradient, is made at large transmembrane proteins called ATP syntheses, represents most of the energy made during respiration.
(all of the above)
Why are both the temperatures and times involved in hot air sterilization higher than those involved in steam sterilization?
Heat transfer is more efficient when water is involved.
At which phase of microbial growth is the growth rate identical to the death rate?
stationary phase
A bacterial growth experiment began with 100 cells and ended with 409,600 cells. How many generations occurred?
12
[Log (409,600) – Log (100)]/log 2 = 12, see Appendix B.
During glycolysis
ATP is generated by substrate-level phosphorylation.
Suppose you have a suspension of C. botulinum endospores that has a decimal reduction time (DRT) of 1.5 minutes at 121 °C. If you had 1 x 10 6 endospores, how long (at 121 °C ) would it take to reduce this number to a single organism?
9 minutes
The process of destroying vegetative pathogens on living tissue is most correctly called
antisepsis
What type of organism would have an optimum growth temperature at about 12 °C?
psychrophile
Plasmas, supercritical fluids, and peroxygens are all
new methods used to sterilize.
The most important products of the Krebs cycle are
NADH and FADH2.
The method of preserving bacterial cultures that involves sublimation is
lyophilization
The germicidal action of chlorine is due to the formation of
hypochlorous acid
The net yield of ATP equivalents from one turn of the Krebs cycle (starting with acetyl-CoA) is
12
The most common physical method of microbial control in foods is
heat treatment or low temperatures.
The most resistant microbe (of the ones listed) to chemical biocides is
bacterial endospores
A bacterostatic agent
inhibits the growth of bacteria.
Flavoproteins, cytochromes, and ubiquinones are all part of
the electron transport chain.
Phenolics, biguanides, halogens, alcohols, and probably quaternary ammonium compounds (Quats) all cause damage to the cell’s
plasma membrane.
Radiation does most of its lethal damage by causing breaks in, or changes to the microbe’s
DNA
Which of the following is not a common end product of a microbial fermentation?
Glucose
Organisms that grow deep in the bottom of the ocean (no light) next to hydrogen sulfide vents (source of energy), and are able to fix CO2 in the seawater, would be referred to as
chemoautotrophs
Which type of organism is indifferent to either the presence or absence of oxygen?
aerotolerant anaerobe
During photosynthesis, the main products of the light-dependent reactions are ________, whereas the main products of light-independent reactions are __________.
ATP, O2, and NADPH/sugars
Enzymes
lower the activation energy of a chemical reaction.
Five bacterial cells with a generation time of 15 minutes were allowed to grow for 8 hours. How many cells are present?
2.15 × 1010
Number of generations = 480/15 = 32; Nt = N0 x 2number of generations, = 5 x 232 = 2.15 x 1010, see Appendix B.
A sample of milk is diluted 1:2,000,000 and 1 ml samples of this dilution are plated in duplicate. The average plate count is 50 CFU. How many CFU/ml are present in the undiluted milk?
100,000,000
Total CFU/ml in milk = Ave. plate count x 1/dilution factor = 50 x 2,000,000 = 100,000,000 CFU/ml.
Blood agar containing an antibiotic that inhibits gram-positive organisms, would most correctly be called
both selective and differential.