Chapter 27, Problem 13TYK

O157:H7, a pathogenic strain of E. coli, has over 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

1. a. this virulent strain has many more R plasmids than does the harmless strain and is resistant to almost all antibiotics.
2. b. at least some of these genes were acquired through phage-mediated horizontal gene transfer.
3. c. virulence genes appear to have been acquired through conjugation with K-12.
4. d. all of the above are correct.