Your textbook describes how the ordinarily harmless bacterium Escherischia coli
ID: 201065 • Letter: Y
Question
Your textbook describes how the ordinarily harmless bacterium Escherischia coli evolved into the dangerously pathogenic strain O157:H7. Sequence analysis of the O157:H7 strain indicates that over 1000 of its ~5400 genes are foreign to the E. coli genome. The most likely explanation for the origin of the O157:H7 strain is
a.conjugation between two strains of E. coli
b.transduction-mediated horizontal gene transfer
c.the rapid rate of reproduction of E. coli
d.the high mutation rate of the E. coli genome
e.natural selection in response to antibody treatment
Explanation / Answer
Virulence factors contributing to the pathogenicity of E. coli O157:H7, including Shiga toxins and intimin are encoded on pathogenicity islands in the O157 chromosome and are thought to have been acquired by horizontal transfer.
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