O157:H7, a pathogenic strain of E. coli, has more than 1,000 genes that are not present in the harmless strain K-12. Many of these genes are associated with phage DNA in the bacterial chromosome. These observations suggest that __________.

a. this virulent strain has many more R plasmids than does the harmless strain and is resistant to almost all antibiotics
b. at least some of these genes were acquired through phage-mediated horizontal gene transfer
c. at least some of these genes were acquired through phage-mediated horizontal gene transfer, and these genes were not acquired through conjugation with K-12
d. these genes were not acquired through conjugation with K-12
e. most of these novel genes must be a result of mutations and short generation times


Answer: c. at least some of these genes were acquired through phage-mediated horizontal gene transfer, and these genes were not acquired through conjugation with K-12

Biology & Microbiology

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