MSHA-like pili of non-toxigenic Vibrio cholerae strains

Abstract

Aim . In this study, we set out to identify the homologues of genes from the msh-cluster in the genomes of non-toxigenic V cholerae, to perform the bioinformatics analysis of their products, as well as to study the adhesive properties of strains containing altered genes. Materials and methods . We analysed 17 clinical strains of non-O1/non-O139 V cholerae and 2 strains of the O1 serogroup isolated from water bodies. Genes belonging to the msh-cluster were identified in the whole genomes using the BLASTN 2.2.29 and BioEdit 7.2.5 programs. Gene translation, comparative analysis of their nucleotide sequences and the amino acid sequences of deduced products were performed using the Vector NTI Advance 11 (Invitrogen). Results and discusssion . In 18 out of the 19 studied genomes we identified gene clusters responsible for production of adhesion pili (mshH-Q) represented by diverse alleles, the majority of which differed from the prototype genes of the msh-cluster in nucleotide composition but had the same localization and arrangement. Only one strain had a cluster that was close to that of the prototype. A bioinformatics analysis of their deduced products indicated that the amino acid sequence of the major MshA pilus subunit is homologous to the prototype only in a short N-terminal region (1-41) while sharing no similarities with the rest of the sequence. Nevertheless, this protein, similar to VcfA described by Kuroki H. et al. (2001) and designated by us as MshA-like, retained a putative pilus domain. A similar pattern was observed in the minor subunits designated as MshC-like. Other minor subunits also retained their characteristic domains. All of the strains agglutinated human erythrocytes (group O) and chicken erythrocytes, and in isolates harboring modified mshA-like and mshC-like genes the reaction was not inhibited by mannose. Since most of the studied strains were isolated from hospitalized patients, it is possible that in non-toxigenic V. cholerae lacking the pathogenicity island VPI, MSHA-like pili may serve as a colonization factor of the human intestine, in contrast to VPI-positive strains. The obtained information provides a basis for experimental verification of this assumption.