Infection with Bacteriophage Led to Loss-of-Function Mutations in FhuA Gene Locus

Abstract

Bacteriophages, also known as phages, are viruses that solely target bacteria for infection and replication. To initiate infection, a phage must bind to a specific receptor on the surface of bacteria. Genetic changes to the genes that encode these surface proteins may block phage attachment, thus, rendering the bacteria resistant to the phage. We hypothesized that when infected with a phage that targets FhuA, Escherichia coli would acquire point mutations, thus allowing the clones to retain the protein’s function while inhibiting infection (Endriss et al., 2003). To test our hypothesis, we isolated bacteriophages from filtered sewage water and generated phage-resistant clones of E. coli. We then isolated genomic DNA from the resistant clones, amplified the fhuA gene by PCR, and Sanger sequenced the DNA for analysis. We discovered that all but one of the phage resistance clones contained frameshift mutations, which eliminates the protein. This finding indicates that E. coli produced non-functional FhuA protein to maintain resistance to phage infection. Since FhuA is an important ferrichrome transporter, we hypothesized that E. coli uses other iron transporters, such as FepA and TonB, to compensate for the loss of FhuA.