UV Stress-Responsive Genes Associated with Enterobacterial Integrative Conjugative Elements of the ICE SXT/R391 Group

SXT/R391-like ICEs are site-specific genome-integrating bacterial mobile elements, frequently isolated from human pathogens, most notably pandemic Vibrio cholerae strains. They encode a range of known advantageous traits, including multiple antibiotic resistance determinants and DNA repair mechanisms. These ICEs have also been found to encode a number of UV-associated phenotypes, including an unusual damage-inducible UV-sensitising phenotype in both prototype members of the family, ICE SXT and ICE R391, as well as many others. This sensitising phenotype, which is recA dependent, was discovered when it was shown that inclusion of an SXT/R391-like ICE within a host genome significantly decreases the post-UV irradiation host cell survival rate. This unusual phenotype would have considerable implications for waterborne host organisms exposed to large amounts of sunlight in tropical areas in which these ICEs frequently reside. Here, we review this unusual damage-inducible phenotype, the surprising nature of the genes involved, and other UV-associated functions of the SXT-R391 family of ICEs.