Exopolysaccharides produced by Streptococcus thermophilus and phage adsorption

FERNANDA MOZZI; CECILIA RODRÍGUEZ; ROEL VAN DER MEULEN; FREDERIC VANINGELGEM; RAÚL RAYA; LUC DE VUYST; GRACIELA FONT DE VALDEZ

Egmond aan Zee, The Netherlands

Simposio; 8th Symposium on Lactic Acid Bacteria. Genetics, Metabolism and Applications; 2005

Federation of European Microbiological Societies. The Netherlands Society for Microbiology

Exopolysaccharide (EPS)-producing lactic acid bacteria contribute to the textural properties of fermented foods. It has been suggested that EPS might protect the cells from detrimental environmental conditions. As lytic phages cause significant problems in the dairy industry, this study was undertaken to determine whether the presence (slime EPS or capsular CPS) and characteristics (chemical composition and molecular mass) of EPS from Streptococcus thermophilus could be involved in bacteriophage adsorption. Eight S. thermophilus strains were evaluated for their ability to produce EPS or CPS and their polymers were characterised. S. thermophilus CRL1190, CRL821 and CRL815 were the only CPS+. The ropy culture phenotype was observed for S. thermophilus CRL1190 and CRL638, which produced high molecular mass polysaccharides. The EPS chemical composition was mainly composed of glucose and galactose and to a lesser extent rhamnose, glucosamine, and galactosamine. All strains were analysed for their phage-host interactions with five specific phages (Ysca, 3, 5, 6, 8). The phages host range and their efficiency of plating (EOP) on each strain were determined. The phages attacked mainly the CPS+ strains. S. thermophilus CRL1190 was the only one sensitive to all bacteriophages with the highest EOP. No relationship was found between the EPS chemical composition and the phage sensitivity/resistance phenotype. A CPS- mutant from S. thermophilus CRL1190 was resistant to phage f3 and less sensitive to the other phages. The phage f3 attacked two out of three CPS+ strains. A further phage adsorption assay suggests that the capsule might be involved in phage adsorption.