Structural Studies on a Cell Wall Polysaccharide Preparation of Lactococcus Lactis Subspecies Cremoris H414

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

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.

Structures of cell-wall glycopolymers of Lactococcus lactis BIM B-1024

Glycopolymers of two types were isolated from the cell wall of Lactococcus lactis BIM B-1024 by stepwise extraction with cold and hot 10% CCl3CO2H and separated by anion-exchange gel chromatography. The following structures of the glycopolymers were established by sugar analysis, dephosphorylation with 48% HF, 1D and 2D NMR spectroscopy, and ESI-MS:

β-D-Galp-(1→4)-β-D-Glcp-(1→6)┐

→4)-β-D-Galp-(1→4)-β-D-Glcp-(1→4)-α-D-Glcp-(1→ PSI

β-D-Glcp-(1→3)┐

→60-α-D-GalpNAc-(1→3)-β-D-GalpNAc-(1→5)-Rib-ol-1-P-(O→ PSII

β-D-Glcp-(1→4)┘

Polysaccharides with the same or similar structures to PSI have been found earlier in various Lactobacillus species, whereas, to our knowledge, the structure of PSII is new.