|Hofmann, Christopher - Vanderbilt University Medical Center|
|Nguyen, Ly Huong|
Submitted to: FEMS Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2016
Publication Date: 5/5/2016
Publication URL: http://handle.nal.usda.gov/10113/5852150
Citation: Uhlich, G.A., Chen, C., Cottrell, B.J., Yan, X., Hofmann, C.S., Nguyen, L.T. 2016. Stx1 prophage excision in Escherichia coli strain PA20 confers strong curli and biofilm formation by restoring native mlrA. FEMS Microbiology Letters. doi: 10.1093/femsle/fnw123.
Interpretive Summary: Shiga toxin-producing Escherichia coli (STEC) are food-borne pathogenic bacteria that include serotype O157:H7, which have been associated with large outbreaks of bloody diarrhea that are often fatal for children, the elderly, and immunocompromised adults. We have previously shown that a bacterial virus often inserts into a regulatory gene that controls biofilm formation (bacteria forming large aggregates on surfaces) and resistance to food-related stress in E. coli serotype O157:H7, severely limiting its ability to survive in the environment. However, small numbers of these virus-infected cells can spontaneously lose the virus. In this study, we show that when the virus is cured from the chromosome of STEC O157:H7, the regulatory gene is reformed, restoring stress resistance. This provides a strong mechanism for increasing the survival and persistence of this important pathogen. This mechanism offers an important new target for developing drugs or virus-based therapies for controlling STEC outbreaks.
Technical Abstract: Prophage insertions in Escherichia coli O157:H7 mlrA contribute to the low expression of curli fimbriae and biofilm observed in many clinical isolates. Varying levels of CsgD-dependent curli/biofilm expression are restored to strains bearing prophage insertions in mlrA by mutation of regulatory genes affecting csgD. Our previous study identified strong biofilm- and curli-producing variants in O157:H7 cultures that had lost the mlrA-imbedded prophage characteristic of the parent population, suggesting prophage excision as a mechanism for restoring biofilm properties. In this study we compared genomic, transcriptomic, and phenotypic properties of parent strain PA20 (stx1, stx2) and its prophage-cured variant, 20R2R (stx2), and confirmed the mechanism underlying the differences in biofilm formation.