RESUMO
Helicobacter pylori NCTC 11637 lipopolysaccharide (LPS) expresses the human blood group antigen Lewis x (Le(x)) in a polymeric form. Le(x) is beta-D-galactose-(1-4)-[alpha-L-fucose-(1-3)]-beta-D-acetylglucosamine. Schematically the LPS structure is (Le(x))n-core-lipid A. In this report, we show that Le(x) expression is not a stable trait but that LPS displays a high frequency (0.2 to 0.5%) of phase variation, resulting in the presence of several LPS variants in one bacterial cell population. One type of phase variation implied the loss of alpha1,3-linked fucose, resulting in variants that expressed nonsubstituted polylactosamines (also called the i antigen), i.e., Le(x) minus fucose; LPS: (lactosamine)n-core-lipid A. The switch of Le(x) to i antigen was reversible. A second group of variants arose by loss of polymeric main chain which resulted in expression of monomeric Le(y); LPS: (Le(y))-core-lipid A. A third group of variants arose by acquisition of alpha1,2-linked fucose which hence expressed Le(x) plus Le(y); LPS: (Le(y))(Le(x))n-core-lipid A. The second and third group of variants switched back to the parental phenotype [(Le(x))-core-lipid A] in lower frequencies. Part of the variation can be ascribed to altered expression levels of glycosyltransferase levels as assessed by assaying the activities of galactosyl-, fucosyl-, and N-acetylglucosaminyltransferases. Clearly phase variation increases the heterogeneity of H. pylori, and this process may be involved in generating the very closely related yet genetically slightly different strains that have been isolated from one patient.
Assuntos
Variação Antigênica , Helicobacter pylori/imunologia , Antígenos CD15/imunologia , Lipopolissacarídeos/imunologia , Amino Açúcares/genética , Amino Açúcares/imunologia , Amino Açúcares/metabolismo , Epitopos/genética , Epitopos/imunologia , Fucosiltransferases/metabolismo , Galactosiltransferases/metabolismo , Glicosiltransferases/metabolismo , Helicobacter pylori/genética , Helicobacter pylori/metabolismo , Antígenos do Grupo Sanguíneo de Lewis/genética , Antígenos do Grupo Sanguíneo de Lewis/imunologia , Antígenos do Grupo Sanguíneo de Lewis/metabolismo , Antígenos CD15/genética , Antígenos CD15/metabolismo , Lipídeo A/imunologia , Lipídeo A/metabolismo , Lipopolissacarídeos/metabolismo , Mimetismo Molecular/genética , Mimetismo Molecular/imunologia , Mutação , N-Acetilglucosaminiltransferases/metabolismo , Polissacarídeos/genética , Polissacarídeos/imunologia , Polissacarídeos/metabolismoRESUMO
24 group C and 31 group G streptococcal strains were studied examining the production of extracellular nucleases, NADase, hyaluronidase and streptolysin O. 5 mucous strains were characterized by diminished growth and lack of hyaluronidase and NADase-production. Regarding the other strains of group C, one half produced nuclease-activity whereas only one out of ten group G streptococci did. Group G streptococci were more active in the production of NADase and hyaluronidase than group C streptococci. The levels of streptolysin O in groups C and G are comparable.
