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Open Access Research article

Heterologous expression of pathogen-specific genes ligA and ligB in the saprophyte Leptospira biflexa confers enhanced adhesion to cultured cells and fibronectin

Cláudio Pereira Figueira1, Julio Croda16, Henry A Choy23, David A Haake23, Mitermayer G Reis1, Albert I Ko14 and Mathieu Picardeau5*

Author Affiliations

1 Oswaldo Cruz Foundation, Brazilian Ministry of Health, Gonçalo Moniz Research Center, Rua Waldemar Falcão, 121, 40295-001 Salvador, Bahia, Brazil

2 Veterans Affairs Greater Los Angeles Health Care System, Division of Infectious Diseases, 111F, 11301 Wilshire Blvd, Los Angeles, CA 90073, California, USA

3 Department of Medicine, University of California Los Angeles School of Medicine, Los Angeles, California, USA

4 Division of Epidemiology of Microbial Diseases, Department of Epidemiology and Public Health, Yale University School of Medicine, Division of Epidemiology of Microbial Disease, 319 LEPH - 60 College St., New Haven, CT 06510 New Haven, USA

5 Institut Pasteur, Unité de Biologie des Spirochètes, 28 rue du docteur Roux, 75724 Paris Cedex 15, France

6 Faculty of Health Sciences, Federal University of Grande Dourados, Brazil

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BMC Microbiology 2011, 11:129  doi:10.1186/1471-2180-11-129

Published: 9 June 2011

Abstract

Background

In comparison to other bacterial pathogens, our knowledge of the molecular basis of the pathogenesis of leptospirosis is extremely limited. An improved understanding of leptospiral pathogenetic mechanisms requires reliable tools for functional genetic analysis. Leptospiral immunoglobulin-like (Lig) proteins are surface proteins found in pathogenic Leptospira, but not in saprophytes. Here, we describe a system for heterologous expression of the Leptospira interrogans genes ligA and ligB in the saprophyte Leptospira biflexa serovar Patoc.

Results

The genes encoding LigA and LigB under the control of a constitutive spirochaetal promoter were inserted into the L. biflexa replicative plasmid. We were able to demonstrate expression and surface localization of LigA and LigB in L. biflexa. We found that the expression of the lig genes significantly enhanced the ability of transformed L. biflexa to adhere in vitro to extracellular matrix components and cultured cells, suggesting the involvement of Lig proteins in cell adhesion.

Conclusions

This work reports a complete description of the system we have developed for heterologous expression of pathogen-specific proteins in the saprophytic L. biflexa. We show that expression of LigA and LigB proteins from the pathogen confers a virulence-associated phenotype on L. biflexa, namely adhesion to eukaryotic cells and fibronectin in vitro. This study indicates that L. biflexa can serve as a surrogate host to characterize the role of key virulence factors of the causative agent of leptospirosis.