Surface displaced alfa-enolase of <it>Lactobacillus plantarum </it>is a fibronectin binding protein

• Main Authors: Muscariello Lidia, Vici Manuela, Candela Marco, Siciliano Rosa, Vastano Valeria, Castaldo Cristiana, Marasco Rosangela, Sacco Margherita
• Format: Article
• Language: English
• Published: BMC 2009-02-01
• Series: Microbial Cell Factories
• Online Access: http://www.microbialcellfactories.com/content/8/1/14

<p>Abstract</p> <p>Background</p> <p>Lactic acid bacteria of the genus <it>Lactobacillus </it>and <it>Bifidobacterium </it>are one of the most important health promoting groups of the human intestinal microbiota. Their protective role within the gut consists in out competing invading pathogens for ecological niches and metabolic substrates. Among the features necessary to provide health benefits, commensal microorganisms must have the ability to adhere to human intestinal cells and consequently to colonize the gut. Studies on mechanisms mediating adhesion of lactobacilli to human intestinal cells showed that factors involved in the interaction vary mostly among different species and strains, mainly regarding interaction between bacterial adhesins and extracellular matrix or mucus proteins. We have investigated the adhesive properties of <it>Lactobacillus plantarum</it>, a member of the human microbiota of healthy individuals.</p> <p>Results</p> <p>We show the identification of a <it>Lactobacillus plantarum </it>LM3 cell surface protein (48 kDa), which specifically binds to human fibronectin (Fn), an extracellular matrix protein. By means of mass spectrometric analysis this protein was identified as the product of the <it>L. plantarum enoA1 </it>gene, coding the EnoA1 alfa-enolase. Surface localization of EnoA1 was proved by immune electron microscopy. In the mutant strain LM3-CC1, carrying the <it>enoA1 </it>null mutation, the 48 kDa adhesin was not anymore detectable neither by anti-enolase Western blot nor by Fn-overlay immunoblotting assay. Moreover, by an adhesion assay we show that LM3-CC1 cells bind to fibronectin-coated surfaces less efficiently than wild type cells, thus demonstrating the significance of the surface displaced EnoA1 protein for the <it>L. plantarum </it>LM3 adhesion to fibronectin.</p> <p>Conclusion</p> <p>Adhesion to host tissues represents a crucial early step in the colonization process of either pathogens or commensal bacteria. We demonstrated the involvement of the <it>L. plantarum </it>Eno A1 alfa-enolase in Fn-binding, by studying LM3 and LM3-CC1 surface proteins. Isolation of LM3-CC1 strain was possible for the presence of expressed <it>enoA2 </it>gene in the <it>L. plantarum </it>genome, giving the possibility, for the first time to our knowledge, to quantitatively compare adhesion of wild type and mutant strain, and to assess doubtless the role of <it>L. plantarum </it>Eno A1 as a fibronectin binding protein.</p>