Chapter 7 - Microbial Growth

Most bacterial and archaeal cells divide by A. mitosis B. meiosis C. binary fission D. all of these

Which of the following is the correct order for binary fission? A. "A septum forms at midcell, the cell elongates, replicates its chromosome, and separates the chromosome into the two parts of the cell." B. "The cell elongates, a septum forms at midcell, the cell replicates its chromosome, and separates the chromosome into the two parts of the cell." C. "The cell elongates, replicates its chromosome, and separates the chromosome into the two parts of the cell, and a septum forms at midcell." D. None of these.

The __________ is a group of proteins needed for DNA synthesis that assembles at the origin of replication. A. septum B. replisome C. prospore D. none of these

The process of forming a cross wall between two daughter cells is known as A. replication B. septation C. sporulation D. mitosis

The site at which replication of DNA starts in bacterial cells is known as the __________. A. origin of replication B. replisome C. terminus D. z-ring

The actin-like protein that seems to be involved in determining cell shape is A. MreB. B. ActA. C. SpnC. D. FtsZ.

"During cytokinesis, a critical step in septation is the assembly of the " A. replisome. B. spindle body. C. Z ring. D. cytoskeletal spiral.

Organisms that grow well at 0C and have optimum growth temperatures of 15C or lower are called A. pyrotrophs. B. psychrophiles. C. frigiphiles. D. mesophiles.

Organisms that do not require oxygen for growth but grow better in its presence are called A. facultative anaerobes. B. microaerophiles. C. aerotolerant. D. anoxygenic.

Organisms that are damaged by the normal atmospheric levels of oxygen (20%) but require oxygen at levels of 2 10% for growth are called A.facultative anaerobes. B. microaerophiles. C. aerotolerant. D. anoxygenic.

Most microorganisms maintain their internal pH A. near neutral (pH 7). B. near their optimum growth pH. C. slightly acidic (pH 4 6). D. slightly alkaline (pH 8 10).

Organisms that have their optimum growth pH between 8.5 and 11.5 are called __________. A. acidophiles B. alkaliphiles C. pyrophiles D. barophiles

Complex microbial communities that grow tightly adhered to surfaces are called __________. A. polysaccharide clusters B. growth communities C. film residues D. biofilms

Quorum sensing A. is a phenomenon in which bacteria monitor their own population density. B. depends on the sensing of signal protein molecules. C. plays an important role in formation of biofilms by Pseudomonas aeruginosa. D. all of the choices

Which of the following can be used to isolate pure cultures of bacteria from mixtures? A. spread plates B. streak plates C. pour plates D. all of the choices

Media containing some ingredients of unknown chemical composition are called __________ media. A. undefined B. complex C. defined D. synthetic

A growth medium that favors the growth of some microorganisms but inhibits the growth of other microorganisms is a __________ medium. A. selective B. differential C. selective and differential D. neither selective nor differential

A growth medium that distinguishes among different groups of bacteria on the basis of their biological characteristics is called a __________ medium. A. selective B. differential C. enrichment D. transport

"Mannitol salt agar (MSA) only allows the growth of halophiles (salt-loving microbes); nonhalophiles will not grow. Among the halophiles, mannitol fermenters will produce acid that turns the pH indicator yellow; mannitol nonfermenters leave the medium red. Onto MSA you inoculate a halophilic mannitol fermenter and a halophilic mannitol nonfermenter. In this case, the medium is acting as (a) __________ medium/" A. selective B. differential C. selective and differential D. enrichment

"Mannitol salt agar (MSA) only allows the growth of halophiles (salt-loving microbes). Among the halophiles, mannitol fermenters release acid that turns the pH indicator yellow; mannitol nonfermenters leave the medium red. Onto MSA you inoculate a halophilic mannitol nonfermenter and a nonhalophilic mannitol nonfermenter. Here the medium acts as a __________ medium. " A. selective B. differential C. selective and differential D. enrichment

Media in which all components and their concentration are known are called __________ media. A. transport B. defined C. selective D. enrichment

The total number of viable microorganisms remains constant in stationary phase because A. there is a balance between cell division and cell death. B. there is a cessation of cell division even though the cells may remain metabolically active. C. either there is a balance between cell division and cell death or there is a cessation of cell division even though the cells may remain metabolically active. D. none of the choices

Cells may enter stationary phase because of A. the depletion of an essential nutrient. B. a lack of available oxygen. C. the accumulation of toxic waste products. D. all of the choices

Which of these methods can be used to determine the number of viable microorganisms in a sample? A. Light scattering in a spectrophotometer. B. Measuring total cell mass. C. Measuring colony forming units per ml. D. Counting a known volume of cells in a hemocytometer.

Microorganisms are most nearly uniform in terms of chemical and physiological properties during __________ phase. A. lag B. exponential C. stationary D. decline

Which of the following is a reason for the occurrence of a lag phase in a bacterial growth curve? A. "The cells may be old and depleted of ATP, essential cofactors, and ribosomes that must be synthesized before growth can begin." B. The medium may be different from the previous growth medium so that the cells must synthesize new enzymes to use different nutrients. C. The organisms may have been injured and require time to recover. D. All of these are potential reasons.

"If all cell components are synthesized at constant rates relative to one another, the culture is said to be in __________ growth; however, if the rates of synthesis of some components change relative to the rates of synthesis of other components, the culture is said to be in __________ growth. " A. unbalanced; balanced B. balanced; unbalanced

"Given a log phase bacterial culture with 1 x 10^6 cells per ml and a generation time of 30 minutes, how long does it take the culture to reach a density of 6.4x 10^7 cells per ml? " A. 1 hour B. 2 hours C. 3 hours D. 4 hours

"At 4:00 p.m. a closed flask of sterile broth is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the log phase culture has population of 65 million cells. The approximate number of generations that has occurred is" A. 5 B. 13 C. 21 D. 27

"At 4:00 p.m. a closed flask of sterile broth is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the log phase culture has a population of 65 million cells. The mean generation time is approximately" A. 10 minutes B. 20 minutes. C. 30 minutes. D. 40 minutes.

Most microorganisms maintain their internal pH A. near neutral (pH 7). B. near their optimum growth pH. C. slightly acidic (pH 4 6). D. slightly alkaline (pH 8 10).