For what purpose do bacteria use restriction enzymes?
A. They are used in plasmid exchanges to fuse plasmid DNA.
B. They are used to restrict important nutrients from leaving the bacterial cell.
C. They are used to resist infections by viruses.
D. They are used to cut up and recycle mRNA transcripts.
E. They are used to attach amino acids to tRNA molecules.
C
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On MacConkey agar, Serratia spp. would appear:
a. red. b. colorless. c. green. d. yellow.
The earth's earliest atmosphere was likely
composed mostly of gaseous a. hydrogen. b. nitrogen. c. water vapor. d. carbon dioxide. e. mixtures of these
Which of the following statements is true about the decolorizing step for the acid-fast stain?
A) Because acid-fast bacteria have a waxy cell wall that resists decolorization by the acetone-alcohol rinse, they appear a deep blue at the end of the procedure. B) Over-decolorizing can lead to false-positive results. C) Acetone-alcohol solution is the decolorizing agent. D) The decolorizing step is the differentiating step. E) Non-acid-fast bacteria appear bright pink-red at the end of the procedure.
Which of the following may be a component of bacterial cell walls?
A. carrageenan B. lipoteichoic acids C. mycolic acid D. tubulin E. both lipoteichoic and mycolic acids