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Intracellular D-serine accumulation promotes genetic diversity via modulated induction of RecA in enterohemorrhagic Escherichia coli

Lookup NU author(s): Dr James ConnollyORCiD


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© 2016, American Society for Microbiology. We recently discovered that exposure of enterohemorrhagic Escherichia coli (EHEC) to D-serine resulted in accumulation of this unusual amino acid, induction of the SOS regulon, and downregulation of the type III secretion system that is essential for efficient colonization of the host. Here, we have investigated the physiological relevance of this elevated SOS response, which is of particular interest given the presence of Stx toxin-carrying lysogenic prophages on the EHEC chromosome that are activated during the SOS response. We found that RecA elevation in response to D-serine, while being significant, was heterogeneous and not capable of activating stx expression or stx phage transduction to a nonlysogenic recipient. This "SOS-like response" was, however, capable of increasing the mutation frequency associated with low-level RecA activity, thus promoting genetic diversity. Furthermore, this response was entirely dependent on RecA and enhanced in the presence of a DNA-damaging agent, indicating a functional SOS response, but did not result in observable cleavage of the LexA repressor alone, indicating a controlled mechanism of induction. This work demonstrates that environmental factors not usually associated with DNA damage are capable of promoting an SOS-like response. We propose that this modulated induction of RecA allows EHEC to adapt to environmental insults such as D-serine while avoiding unwanted phage-induced lysis.

Publication metadata

Author(s): Connolly JPR, Roe AJ

Publication type: Article

Publication status: Published

Journal: Journal of Bacteriology

Year: 2016

Volume: 198

Issue: 24

Pages: 3318-3328

Print publication date: 01/12/2016

Online publication date: 18/11/2016

Acceptance date: 27/09/2016

ISSN (print): 0021-9193

ISSN (electronic): 1098-5530

Publisher: American Society for Microbiology


DOI: 10.1128/JB.00548-16

PubMed id: 27698085


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