Ecology of Exopolysaccharide Formation by Lactic Acid Bacteria: Sucrose Utilisation, Stress Tolerance, and Biofilm Formation
Michael Gänzle and Clarissa Schwab
from: Bacterial Polysaccharides: Current Innovations and Future Trends (Edited by: Matthias Ullrich). Caister Academic Press, U.K. (2009)
Lactic acid bacteria (LAB) synthesise a wide variety of exopolysaccharides (EPS); these polysaccharides are synthesised extracellularly from sucrose by glycansucrases, or intracellularly by glycosyltransferases from sugar nucleotide precursors. This chapter provides an overview on emerging concepts related to the ecological significance of EPS production by LAB. Biofilm formation, stress resistance and sucrose utilisation are clearly linked to the formation of EPS in individual species of LAB. The high frequency of homopolysacharide (HoPS) and heteropolysaccharide (HePS) producing LAB in the oral cavity and intestinal ecosystems argues in favour for an important role of EPS formation for the persistence of LAB in these habitats. The intricate regulatory network controlling the expression of glycansucrases in oral streptococci is in keeping with the contribution of HoPS and extracellular glycansucrases to biofilm formation and persistence in the oral cavity. EPS production by intestinal lactobacilli may play a comparable role. Glycansucrases in Lb. reuteri of HoPS and FOS production are regulated in response to stress sensed by the cytoplasmic membrane. The products of glycansucrases improve survival of lactobacilli in a scenario characterised by strong fluctuations in water activity, temperature, pH, and nutrient supply, and the presence of natural inhibitors. Because the expression of glycansucrases in many strains of lactobacilli and Leuconostoc species is induced by sucrose, the contribution of glycansucrases to sucrose catabolism may be their main ecological role in some strains read more ...