The FUR-like regulators PerRA and PerRB integrate a complex regulatory network that promotes mammalian host-adaptation and virulence of Leptospira interrogans

PLoS Pathog. 2021 Dec 2;17(12):e1009078. doi: 10.1371/journal.ppat.1009078. eCollection 2021 Dec.

Abstract

Leptospira interrogans, the causative agent of most cases of human leptospirosis, must respond to myriad environmental signals during its free-living and pathogenic lifestyles. Previously, we compared L. interrogans cultivated in vitro and in vivo using a dialysis membrane chamber (DMC) peritoneal implant model. From these studies emerged the importance of genes encoding the Peroxide responsive regulators PerRA and PerRB. First described in in Bacillus subtilis, PerRs are widespread in Gram-negative and -positive bacteria, where regulate the expression of gene products involved in detoxification of reactive oxygen species and virulence. Using perRA and perRB single and double mutants, we establish that L. interrogans requires at least one functional PerR for infectivity and renal colonization in a reservoir host. Our finding that the perRA/B double mutant survives at wild-type levels in DMCs is noteworthy as it demonstrates that the loss of virulence is not due to a metabolic lesion (i.e., metal starvation) but instead reflects dysregulation of virulence-related gene products. Comparative RNA-Seq analyses of perRA, perRB and perRA/B mutants cultivated within DMCs identified 106 genes that are dysregulated in the double mutant, including ligA, ligB and lvrA/B sensory histidine kinases. Decreased expression of LigA and LigB in the perRA/B mutant was not due to loss of LvrAB signaling. The majority of genes in the perRA and perRB single and double mutant DMC regulons were differentially expressed only in vivo, highlighting the importance of host signals for regulating gene expression in L. interrogans. Importantly, the PerRA, PerRB and PerRA/B DMC regulons each contain multiple genes related to environmental sensing and/or transcriptional regulation. Collectively, our data suggest that PerRA and PerRB are part of a complex regulatory network that promotes host adaptation by L. interrogans within mammals.

Grant support

This work was supported by NIAID grants R21 AI128379 (MC) and R01 AI029735 (MC) as well as research funds provided by Connecticut Children’s Medical Center (MC). EB is supported by the Coordination for the Improvement of Higher Education Personnel (CAPES-PRINT #88887.338735/2019-00). CZA was awarded a grant from the Fondation Etchèbes-Fondation de France (S-CM16008) (https://www.fondationdefrance.org/fr/fondation/fondation-etchebes). This project also was supported by funding from the European Union's Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie grant agreement No 665807. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.