Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2008
Publication Date: 7/16/2008
Citation: Victoria, B., Ahmed, A., Zuerner, R.L., Ahmed, N., Bulach, D.M., Quinteiro, J., Hartskeerl, R.A. 2008. Conservation of the S10-spc-alpha Locus within Otherwise Highly Plastic Genomes Provides Phylogenetic Insight into the Genus Leptospira. PLoS One. 3(7):1-9. Available: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002752.
Interpretive Summary: Leptospirosis is one of the most widespread zoonotic diseases in the world and is caused by pathogenic spirochaetes of the genus Leptospira. Genetic classification of this genus is based on DNA homology. In this study, we examined genetic organization and content of the S10-spc-alpha operon in Leptospira. We demonstrate an unexpected conservation of this operon across all leptospiral genomes. These observations might have important bearing on our perception of Leptospira evolution and adaptation of its variants to different host species and environmental niches.
Technical Abstract: A comparative analysis of the Leptospira interrogans S10-spc-alpha operon was performed by PCR using primer sets covering the whole operon. Correctly sized fragments were obtained by PCR from all of L. interrogans strains for each primer set indicating that the S10-spc-alpha locus is well conserved in this species. Few differences were detected in amplification profiles between different pathogenic species, indicating that this operon is conserved among pathogenic Leptospira. In contrast, PCR analysis of saprophytic Leptospira species and species with an intermediate pathogenic capacity generated varied results. Sequence alignment with known loci of the pathogenic serovars and the saprophytic serovar Patoc (L. biflexa) did not reveal translocations of genes, showing that the S10-spc-alpha operon is conserved within the genus Leptospira and differences observed in PCR profiles likely reflect sequence heterogeneity. Therefore, we hypothesized that variability of PCR products was an indication of variable and conserved coding regions for the genes within this operon. Multilocus sequence typing (MLST) on four loci within the S10-spc-alpha operon was used to characterize phyogenetic relationships among pathogenic Leptospira spp. This analysis resulted in construction of well-defined phylogenetic trees that help resolve questions about the interrelationships of pathogenic Leptospira. Based on the results of analysis of secY sequence data, we found that reliable speciation of pathogenic Leptospira is possible by comparison of a 245 bp region commonly used as a target for diagnostic PCR for leptospirosis.