Identification and analysis of the putative cell wall polysaccharide gene cluster in Streptococcus uberis

Abstract

Streptococcus uberis has a major economic and welfare impact in dairy cattle and a good vaccine for S. uberis mastitis is missing. The current S. uberis vaccine is not very effective and does not provide adequate protection. Therefore, a new approach against S. uberis vaccines is needed. The goals for this study were to identify the RhaCWP biosynthesis gene cluster in S. uberis and to analyze the genetic variation among S. uberis strains. The bacterial strains used in this report were collected from the database GenBank hosted by NCBI. In the human pathogen Streptococcus pyogenes the RhaCWP gene cluster has already been fully characterized. Therefore, we compared the RhaCWP gene cluster in S. pyogenes MGAS5005 with our reference genome, S. uberis NCTC3858, to examine similarities. These results were generated using BLAST and ACT. For the analysis of the genome sequences and gene function annotation Artemis, Pfam, Interpro, and Uniprot were used. The results showed that the putative RhaCWP gene cluster in S. uberis consists of eleven genes, encoding for rhamnose biosynthesis, glycosyltransferase, ABC transporters, membrane proteins, and hypothetical proteins. The RhaCWP gene cluster is not fully conserved among S. uberis strains, only the first four genes and the last gene showed a high conservation for all S. uberis strains. For the rest of the genes, more variation was shown. Four different variants of the RhaCWP gene cluster in S. uberis were determined that had different genes but with similar functions. Based on the variation in the genetic organization of the RhaCWP gene cluster it is expected that the RhaCWP molecule is also different among the variants. Therefore, the RhaCWP molecule in S. uberis is predicted not to be useful as a broadly protective vaccine antigen.