| Abstract |
Gram-positive bacterial biomembranes are composed of phosphatidyl glycerol (PG), cardiolipin (CL), and dihexaosyl diglycerides (DH-DG) as the major lipid constituents. The carbohydrate structures of DH-DG are specific to the particular bacterial species and we previously revealed them to have immunologically active properties. To characterize the species-structure relationship of glycolipids in Gram-positive bacteria, the structures of DH-DG in Pediococcus pentosaceus (PP) for producing fermented soybean paste (miso) and Tetragenococcus halophilus (TH) for soy sauce were determined in comparison with those in Lactobacillus, Streptococcus and Staphylococcus species. They were shown to be Glcα1-2Glcα1-3'DG (kojibiosyl DG) with 18:1(oleic acid) and 18:1 as the fatty acids for PP, and that with 16:0 (palmitic acid) and 18:1 for TH, and their carbohydrate structures were identical to that in Streptococcus salivarius, a symbiotic bacterium in the human oral cavity. Additionally, both bacteria contained an acidic glycolipid, in which glycerol phosphate was attached to the 6-position of the nonreducing terminal Glc residue of DH-DG. TLC immunostaining with human sera revealed antibodies to Galα1-2Glcα1-3'DG (LacDH-DG) from Lactobacillus species and Glcβ1-6Glcβ1-3'DG (StaDH-DG) from Staphylococcus species, but not to Glcα1-2Glcα1-3'DG (StrDH-DG) from Streptococcus species, in 2 out of 20 human sera. Given that one serum sample with anti-StaDH-DG antibodies was from a patient who had suffered from food poisoning due to Staphylococcus aureus 6 months previously, the antibodies to bacterial DH-DG were thought to have arisen via bacterial infection.
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