UC San Diego

Select species of the bacterial genus Leptospira are causative agents of leptospirosis, an emerging global zoonosis affecting nearly one million people worldwide annually. We examined two Leptospira pathogens, L. interrogans serovar Lai str. 56601 and L. borgpetersenii serovar Hardjo-bovis str. L550, as well as the free-living leptospiral saprophyte, L. biflexa serovar Patoc str. 'Patoc 1 (Ames)'. The transport proteins of these leptospires were identified and compared through bioinformatics to determine which proteins are related to pathogenesis, and saprophytism. L. biflexa possesses a disproportionately high number of secondary carriers for metabolic uptake flexibility and environmental adaptability, as well as an increased number of inorganic cation transporters providing ionic homeostasis and effective osmoregulation in a rapidly changing environment. L. interrogans and L. borgpetersenii possess remarkably similar transporter proteomes (transportomes), with near-equivalent representation in most transporter families. The Leptospira pathogens possess complete sphingomyelinases, holins, and virulent outer membrane porins. These transport-related virulence factors, in conjunction with decreased transporter substrate versatility, indicates that pathogenicity arose in Leptospira as a result of progressively narrowing ecological niches and the emergence of a limited set of proteins responsible for host invasion. The variability of host tropism and mortality rates by infectious leptospires suggests that small differences in individual sets of proteins play important physiological and morphological roles