Bacteriocins are target specific toxin proteins produced by bacteria which can inhibit the growth of other bacteria of the same species or closely related species. Bacteriocins produced by Escherichia coli have been well studied and the species were frequently used as a model organism for studying the ecological role of bacteriocins in microbial community. However, the E. coli strains used in previous studies mostly comprised human and animal-associated strains. E. coli were also frequently recovered from other non-host associated environments and some strains were found to be phenotypically indistinguishable but genetically distinct from the commensal strains. These strains were later described as cryptic Escherichia species. In this study, we investigate the bacteriocinogeny o...[ Read more ]

Bacteriocins are target specific toxin proteins produced by bacteria which can inhibit the growth of other bacteria of the same species or closely related species. Bacteriocins produced by Escherichia coli have been well studied and the species were frequently used as a model organism for studying the ecological role of bacteriocins in microbial community. However, the E. coli strains used in previous studies mostly comprised human and animal-associated strains. E. coli were also frequently recovered from other non-host associated environments and some strains were found to be phenotypically indistinguishable but genetically distinct from the commensal strains. These strains were later described as cryptic Escherichia species. In this study, we investigate the bacteriocinogeny of environmental E. coli and cryptic Escherichia species to gain better understanding in the role of bacteriocins in bacteria persisting in marine sediments. E. coli isolates from cow faeces were included in the study as representative of commensal strains. Phenotypic screening assays were used to screen for bacteriocin producers and molecular detection method were used to identify the bacteriocin genes present in the tested isolates. Bacteriocinogeny were found to be prevalent in commensal isolates while environmental isolates showed lower level of bacteriocinogeny. Distinct bacteriocin genotypes were observed between commensal and environmental isolates. This suggests that the habitat may positively select for certain types of bacteriocins. Isolates with bacteriocin genes but did not exhibit bacteriocin activity were found and we hypothesize that the bacteriocin genes might be used for providing immunity towards bacteriocins. Indeed, cross-inhibition assay results depicted that isolates with bacteriocin genes exhibit lower bacteriocin susceptibility. The comparative study of bacteriocinogeny in E. coli isolates from different habitats has provided more information on the ecological role of bacteriocins in a non-host associated environment.