Determinants of enterococcal tolerance against lactobacilli identified by TnSeq

Enterococcus faecalis is a commensal bacterium in human gastrointestinal and urogenital tracts and a leading cause of opportunistic infections. Despite the pathogenic potential of enterococci and the understanding that colonization at these ecological niches, involves intricate mechanisms of interactions with other commensal residents, our understanding of enterococcal interactions in the female vaginal tract remain limited. Therefore, we used transposon sequencing (TnSeq) to interrogate the genome of E. faecalis OG1RF for tolerance determinants during co-culture with Lactobacillus crispatus in vitro. E. faecalis OG1RF is a plasmid-free strain that contains few mobile elements yet retains the robust survival characteristics, intrinsic antibiotic resistance, and virulence traits characteristic of most E. faecalis genotypes. A pool of 6,829 Tn mutants chosen for maximal genomic coverage was used in an approach termed SMarT (Sequence-defined Mariner Technology) TnSeq to identify genetic determinants of tolerance against L. crispatus.