Structural studies of the deacylated glycolipids and lipoteichoic acid of Lactococcus cremoris 3107

Abstract

Lactococcus cremoris and Lactococcus lactis are among the most extensively exploited species of lactic acid bacteria in dairy fermentations. The cell wall of lactococci, like other Gram-positive bacteria, possesses a thick peptidoglycan layer, which may incorporate cell wall polysaccharides (CWPS), wall teichoic acids (WTA), and/or lipoteichoic acids (LTA). In this study, we report the isolation, purification and structural analysis of the carbohydrate moieties of glycolipids (GL) and LTA of the L. cremoris model strain 3107. Chemical structures of these compounds were studied by chemical methods, NMR spectroscopy and positive and negative mode ESI MS. We found that the LTA of strain 3107 is composed of short chains of 1,3-polyglycerol phosphate (PGP), attached to O-6 of the non-reducing glucose of the kojibiose-Gro backbone of the glycolipid anchor. Extraction of cells with cold TCA afforded the detection of 1,3-glycerol phosphate chains randomly substituted at O-2 of glycerol by D-Ala. Unlike the LTA of L. lactis strains studied to date, the PGP backbone of the LTA of L. cremoris 3107 did not carry any glycosyl substitution. The deacylated glycolipid fraction contained the free kojibiose-Gro oligosaccharide, identical to the backbone of the GL anchor of LTA, and its shorter fragment α-Glc-1-Gro. These OS may have originated from the GL precursors of LTA biosynthesis.

Keywords: Cell walls; Glycolipids; Lactic acid bacteria; Lactococcus cremoris 3107; Lipoteichoic acid; NMR.