Horizontal transfer of therfbcluster inLeptospirais a genetic determinant of serovar identity

Abstract

Leptospirabacteria comprise numerous species, several of which cause serious disease to a broad range of hosts including humans. These spirochetes exhibit large intraspecific variation, resulting in complex tabulations of serogroups/serovars that crisscross the species classification. Serovar identity, linked to biological/clinical phenotypes, depends on the structure of surface-exposed LPS. Many LPS biosynthesis–encoding genes reside within the chromosomicrfbgene cluster. However, the genetic basis of intraspecies variability is not fully understood, constraining diagnostics/typing methods to cumbersome serologic procedures. We now show that the gene content of therfbcluster strongly correlates withLeptospiraserovar designation. Whole-genome sequencing of pathogenicL. noguchii, including strains of different serogroups, reveals that therfbcluster undergoes extensive horizontal gene transfer. Therfbclusters from severalLeptospiraspecies disclose a univocal correspondence between gene composition and serovar identity. This work paves the way to genetic typing ofLeptospiraserovars, and to pinpointing specific genes within the distinctrfbclusters, encoding host-specific virulence traits. Further research shall unveil the molecular mechanism ofrfbtransfer amongLeptospirastrains and species.