Escherichia coli is a natural inhabitant of the gastrointestinal tract of warm-blooded animal. Its persistence in the external environment has been associated with negative impacts on our lives, and questions on how E. coli were able to expand its niche to the environment have been brought up. It is well known that prophages (i.e. DNA of phages residing in the genome of bacterial cells) play a significant role in the genome diversification and niche expansion of pathogenic E. coli strains from one host species to another. P2-like prophages were among the most widely distributed prophages in E. coli genome, and have a broad host range within the class of γ-proteobacteria. Building upon a model system that consisted of an environmental E. coli strain harboring a P2-like prophage, a wild t...[ Read more ]

Escherichia coli is a natural inhabitant of the gastrointestinal tract of warm-blooded animal. Its persistence in the external environment has been associated with negative impacts on our lives, and questions on how E. coli were able to expand its niche to the environment have been brought up. It is well known that prophages (i.e. DNA of phages residing in the genome of bacterial cells) play a significant role in the genome diversification and niche expansion of pathogenic E. coli strains from one host species to another. P2-like prophages were among the most widely distributed prophages in E. coli genome, and have a broad host range within the class of γ-proteobacteria. Building upon a model system that consisted of an environmental E. coli strain harboring a P2-like prophage, a wild type fecal E. coli strain, its isogenic lysogen with an extra P2-like prophage acquired from the environmental E. coli, the genetic and phenotypic changes in the lysogen associated with phage infection were studied. Results showed that the P2-like prophage had conferred beneficial genes encoded for super-infection immunity to the host, and the lysogen had exhibited better utilization over different carbon sources than the wild type. Transcriptome analysis also revealed that the lysogen had different transcriptional activities over carbon and amino acid transport and metabolism compared to the wild type under seawater. This study supported the hypothesis that phage-mediated horizontal gene transfer is a possible mechanism for E. coli to get beneficial genes and adapt to the environment and added new knowledge on the functional role of lysogeny on bacterial survival. This research was the first to describe the transcriptional response of E. coli when living under seawater.