Project description:Pathogenic Leptospira spp. are the causative agents of the zoonotic disease leptospirosis. During infection, Leptospira are confronted with deadly reactive oxygen species (ROS). Withstanding ROS produced by the host innate immunity is an important strategy evolved by pathogenic Leptospira for persisting in and colonizing hosts. The peroxide stress regulator, PerR, represses genes involved in ROS defenses in L. interrogans. We have performed RNA sequencing in WT and perR mutant strains to characterize the L. interrogans adaptive response to hydrogen peroxide. We showed that Leptospira solicit three main peroxidase machineries (catalase, cytochrome C peroxidase and peroxiredoxin) and heme to adapt to peroxide stress as well as canonical chaperones of the heat shock response, and DNA repair. Determining the PerR regulon allowed to identify the PerR-dependent mechanisms of the peroxide adaptive response and has revealed a regulatory network involving other transcriptional regulators, two-component systems and sigma factors as well as non-coding RNAs that putatively orchestrate, in concert with PerR, this adaptive response. Our findings provide comprehensive insight into the mechanisms required by pathogenic Leptospira to overcome infection-related oxidants. This will participate in framing future hypothesis-driven studies to identify and decipher novel virulence mechanisms.
Project description:Leptospirosis is a global zoonotic, neglected tropical disease. Interestingly, a high level of species specificity (both bacteria and host) plays a major role in the severity of disease presentation which can vary from asymptomatic to multi-organ failure. Pathogenic Leptospira colonize the kidneys of infected individuals and are shed in urine into the environment where they can survive until they are contracted by another host. This study looks at two strains of L. borgpetersenii, HB203 and JB197 which are genetically very similar, and identical by serotyping as serovar Hardjo, yet HB203 causes a chronic infection in the hamster while JB197 causes organ failure and mortality. To better characterize bacterial factors causing different disease outcomes, we examined the gene expression profile of these strains in the context of temperatures that would reflect natural Leptospira life cycles (environmentally similar 29oC and 37oC which is more indicative of host environment). We found vast differences in gene expression both between the strains and within strains between temperatures. Characterization of the transcriptome of L. borgpetersenii serovar Hardjo strains JB197 and HB203 provides insights into factors that can determine acute versus chronic disease in the hamster model of infection. Additionally, these studies highlight strain to strain variability within the same species, and serovar, at different growth temperatures, which needs to be considered when serovars are selected and propagated for use as bacterin vaccines used to immunize domestic animal species.
Project description:Leptospira are emerging zoonotic pathogens transmitted from animals to humans typically through contaminated environmental sources of water and soil. Transcriptional regulation of pathogenic Leptospira spp. underlying the adaptive response to different hosts and environmental conditions remains elusive. In this study, we provide the first global Transcriptional Start Site (TSS) map of a Leptospira species. RNA was obtained from the pathogen Leptospira interrogans grown at 30° (optimal in vitro temperature) and 37°C (host temperature) and selectively enriched for 5' ends of native transcripts. Primary TSS (pTSS) was identified for 2,865 genes, accounting for 67% of the total genome. The majority of the TSSs were located between 0 to 10 nucleotides from the translational start site. Comparative dRNA-seq analysis revealed conservation of most pTSS at 30° and 37°C. Promoter prediction algorithms allow the identification of the binding sites of the alternative sigma factor sigma 54. However, other motifs were not identified indicating that Leptospira consensus promoter sequences are inherently different from the E. coli model. RNA sequencing also identified 277 and 226 putative small regulatory RNAs (sRNAs) at 30°C and 37°C, respectively, including 8 validated sRNAs by Northern blots. These results provide the first global view of transcriptional start sites and the repertoire of sRNAs in L. interrogans, and will establish a foundation for future experimental work on gene regulation under various environmental conditions including those in the host.
Project description:Our data demonstrate the suitability of target capture technology for purifying very low quantities of Leptospira DNA from biological samples where the human genome is in vast excess. This enables deep sequencing of partial Leptospira genomes directly from clinical samples using next generation technologies and genotyping.