The oxidative stress response of pathogenic Leptospira is controlled by two peroxide stress regulators which putatively cooperate in controlling virulence.

Crispin Zavala-Alvarado,Odile Sismeiro,Nadia Benaroudj,Hugo Varet,Frédéric J Veyrier,Giovanni Bussotti,Rachel Legendre,Antony T Vincent,Mathieu Picardeau,Jean-Yves Coppée,Pierre Lechat,Céline Lorioux,Samuel G Huete

doi:10.1371/journal.ppat.1009087

Abstract

Pathogenic Leptospira are the causative agents of leptospirosis, the most widespread zoonotic infectious disease. Leptospirosis is a potentially severe and life-threatening emerging disease with highest burden in sub-tropical areas and impoverished populations. Mechanisms allowing pathogenic Leptospira to survive inside a host and induce acute leptospirosis are not fully understood. The ability to resist deadly oxidants produced by the host during infection is pivotal for Leptospira virulence. We have previously shown that genes encoding defenses against oxidants in L. interrogans are repressed by PerRA (encoded by LIMLP_10155), a peroxide stress regulator of the Fur family. In this study, we describe the identification and characterization of another putative PerR-like regulator (LIMLP_05620) in L. interrogans. Protein sequence and phylogenetic analyses indicated that LIMLP_05620 displayed all the canonical PerR amino acid residues and is restricted to pathogenic Leptospira clades. We therefore named this PerR-like regulator PerRB. In L. interrogans, the PerRB regulon is distinct from that of PerRA. While a perRA mutant had a greater tolerance to peroxide, inactivating perRB led to a higher tolerance to superoxide, suggesting that these two regulators have a distinct function in the adaptation of L. interrogans to oxidative stress. The concomitant inactivation of perRA and perRB resulted in a higher tolerance to both peroxide and superoxide and, unlike the single mutants, a double perRAperRB mutant was avirulent. Interestingly, this correlated with major changes in gene and non-coding RNA expression. Notably, several virulence-associated genes (clpB, ligA/B, and lvrAB) were repressed. By obtaining a double mutant in a pathogenic Leptospira strain, our study has uncovered an interplay of two PerRs in the adaptation of Leptospira to oxidative stress with a putative role in virulence and pathogenicity, most likely through the transcriptional control of a complex regulatory network.

Highlights

Pathogenic Leptospira spp. are aerobic diderm bacteria of the spirochetal phylum that are the causative agents of leptospirosis, the most widespread zoonosis [1]
In addition to the Leptospira PerRA regulator that represses defenses against peroxide, we have identified and characterized a second peroxide stress regulator (PerR) regulator in pathogenic Leptospira species (PerRB) that participates in Leptospira tolerance to superoxide
Phenotypic and transcriptomic analyses of single PerRA and PerRB mutants suggest that the two PerRs fulfill distinct functions in the adaptation to oxidative stress

Summary

Introduction

Pathogenic Leptospira spp. are aerobic diderm bacteria of the spirochetal phylum that are the causative agents of leptospirosis, the most widespread zoonosis [1]. More than one million cases of leptospirosis are currently estimated annually in the world, with about 59000 deaths [2]. This disease is considered as a health threat among impoverished populations in developing countries under tropical areas [2], but the number of reported cases of leptospirosis are on the rise in developed countries under temperate climates [3]. Rodents are asymptomatic reservoir for leptospires as the bacteria colonize the proximal renal tubules of these animals. Because of the lack of efficient tools for genetic manipulation of Leptospira spp. and their fastidious growth in the laboratory conditions, our understanding of the mechanism of pathogenicity and virulence as well as the basic biology of these pathogens have been greatly hampered [4,5]

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