Biofilm as an environment for dissemination of stx genes by transduction

Abstract

Dissemination of Shiga toxin (Stx)-encoding bacteriophages is the most likely mechanism for the spread of Stx-encoding genes and the emergence of new Stx-producing Escherichia coli (STEC). Biofilm has been reported to be a place where horizontal gene transfer by plasmid conjugation and DNA transformation may occur, and in this study, horizontal gene transfer by transduction has been demonstrated. Transfer of Stx-encoding bacteriophages to potentially pathogenic E. coli in biofilm was observed at both 20°C and 37°C. The infection rates were higher at 37°C than at 20°C. To our knowledge, this study is the first to show lateral gene transfer in biofilm mediated by a temperate bacteriophage. The study shows that the biofilm environment can be suitable for transduction events and can thereby be an environment for the emergence of new pathogenic E. coli.

Fig 1

Donors, recipients, and transductants in the biofilm at 37°C, shown as mean log₁₀ CFU throughout the experiment period. The bars show standard deviations.

Fig 2

Donors, recipients, and transductants in the biofilm at 20°C, shown as mean log₁₀ CFU throughout the experiment period. The bars show standard deviations.