Investigating the role of the carbon storage regulator A (CsrA) in Leptospira spp.

Theerapat Phoka,Juliana Pipoli Da Fonseca,Mathieu Picardeau,Kanitha Patarakul,Thomas Cokelaer,Lenka Fule

doi:10.1371/journal.pone.0260981

Theerapat Phoka, Juliana Pipoli Da Fonseca + Show 4 more

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https://doi.org/10.1371/journal.pone.0260981

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Journal: PloS one	Publication Date: Dec 13, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: Chulalongkorn University, Institut Pasteur

Abstract

Carbon Storage Regulator A (CsrA) is a well-characterized post-transcriptional global regulator that plays a critical role in response to environmental changes in many bacteria. CsrA has been reported to regulate several metabolic pathways, motility, biofilm formation, and virulence-associated genes. The role of csrA in Leptospira spp., which are able to survive in different environmental niches and infect a wide variety of reservoir hosts, has not been characterized. To investigate the role of csrA as a gene regulator in Leptospira, we generated a L. biflexa csrA deletion mutant (ΔcsrA) and csrA overexpressing Leptospira strains. The ΔcsrA L. biflexa displayed poor growth under starvation conditions. RNA sequencing revealed that in rich medium only a few genes, including the gene encoding the flagellar filament protein FlaB3, were differentially expressed in the ΔcsrA mutant. In contrast, 575 transcripts were differentially expressed when csrA was overexpressed in L. biflexa. Electrophoretic mobility shift assay (EMSA) confirmed the RNA-seq data in the ΔcsrA mutant, showing direct binding of recombinant CsrA to flaB3 mRNA. In the pathogen L. interrogans, we were not able to generate a csrA mutant. We therefore decided to overexpress csrA in L. interrogans. In contrast to the overexpressing strain of L. biflexa, the overexpressing L. interrogans strain had poor motility on soft agar. The overexpressing strain of L. interrogans also showed significant upregulation of the flagellin flaB1, flaB2, and flaB4. The interaction of L. interrogans rCsrA and flaB4 was confirmed by EMSA. Our results demonstrated that CsrA may function as a global regulator in Leptospira spp. under certain conditions that cause csrA overexpression. Interestingly, the mechanisms of action and gene targets of CsrA may be different between non-pathogenic and pathogenic Leptospira strains.

Highlights

Leptospira spp. are gram-negative, spiral-shaped bacteria categorized into non-pathogenic and pathogenic strains
The csrA locus is conserved in the pathogen L. interrogans serovar Manilae and the saprophyte L. biflexa serovar Patoc; the csrA forms with the flagellar genes to develop an operon-like structure (Fig 1A)
Leptospira spp. are ubiquitous bacteria found as free-living saprophytes in environmental water and soil or as pathogens excreted in the urine of asymptomatic hosts to cause disseminated infections in both humans and animals

Summary

Introduction

Leptospira spp. are gram-negative, spiral-shaped bacteria categorized into non-pathogenic and pathogenic strains. Omics studies revealed the changes in gene expression profiles in Leptospira in response to different environmental conditions such as temperature shift [7], physiologic osmolarity [8], serum exposure [9], iron limitation [10], in vivo cultivation on dialysis membrane chamber [11], and in the presence of biofilm [12]. These transcriptome studies highlighted the role of global gene regulation which is a crucial process employed by the bacteria to deal with the changes in the environment. All leptospiral genomes possess a gene that encodes the putative CsrA [18,19,20]

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