Glycerolphosphate-containing cell wall polysaccharides from Streptococcus sanguis

Discovery of glycerol phosphate modification on streptococcal rhamnose polysaccharides

Cell wall glycopolymers on the surface of Gram-positive bacteria are fundamental to bacterial physiology and infection biology. Here we identify gacH, a gene in the Streptococcus pyogenes group A carbohydrate (GAC) biosynthetic cluster, in two independent transposon library screens for its ability to confer resistance to zinc and susceptibility to the bactericidal enzyme human group IIA-secreted phospholipase A₂. Subsequent structural and phylogenetic analysis of the GacH extracellular domain revealed that GacH represents an alternative class of glycerol phosphate transferase. We detected the presence of glycerol phosphate in the GAC, as well as the serotype c carbohydrate from Streptococcus mutans, which depended on the presence of the respective gacH homologs. Finally, nuclear magnetic resonance analysis of GAC confirmed that glycerol phosphate is attached to approximately 25% of the GAC N-acetylglucosamine side-chains at the C6 hydroxyl group. This previously unrecognized structural modification impacts host-pathogen interaction and has implications for vaccine design.

Phosphatidyl glycerolphosphate serves as glycerolphosphate donor in polymer synthesis

Phosphatidyl glycerolphosphate was found to serve as the glycerolphosphate donor for polymer synthesis. When CDP-diglyceride and radiolabeled glycerolphosphate were incubated with the membrane enzyme prepared from Streptococcus sanguis, active syntheses of radiolabeled lipids and polymers were observed. The synthesis of polymer was not inhibited by low concentration of unlabeled phosphatidylglycerol. When [3H, 32P]glycerolphosphate was used, the polymer synthesized contained both 3H and 32P. The lipids formed were characterized as phosphatidylglycerol and phosphatidyl glycerolphosphate. The polymers formed from the latter were characterized as lipoteichoic acid like compounds by sodium dodecylsulfate-polyacrylamide gel electrophoresis.

Purification and immunochemical characterization of Streptococcus sanguis serotype I carbohydrate antigen

The serotype-specific antigen of Streptococcus sanguis ST3 (serotype I, biotype A) was extracted, chromatographically purified, and characterized by immunological and chemical methods. The antigen was extracted from purified cell walls with hot trichloroacetic acid, followed by ion-exchange chromatography on a DEAE-Sephadex A-25 column and gel filtration through a Sephadex G-100 column. A peak fraction was obtained that gave a single precipitin band when reacted with anti-type I serum. The type I antigen was a polysaccharide composed of glucose, rhamnose, and N-acetylglucosamine in a molar ratio of 1.4:2.5:1.0. Quantitative precipitin inhibition tests with various haptenic sugars indicated that an alpha-glucosidic linkage is the immunodeterminant of the type I antigen.

Biosynthesis of glucosyl monophosphoryl undecaprenol and its role in lipoteichoic acid biosynthesis

A glucophospholipid was detected in an incubation mixture containing UDP-glucose, MgCl2, ATP, and a particulate enzyme prepared from Streptococcus sanguis. The synthesis of this lipid was inhibited strongly by UDP and moderately by UMP. The molar ratio of glucose to phosphate in the purified lipid was found to be 1:1. Glucose and glucose 1-phosphate were released by mild alkaline hydrolysis of the glucophospholipid. The lipid produced by mild acid degradation of the purified lipid yielded a thin-layer chromatographic profile similar to that of acid-treated undecaprenol. One of the minor components exhibited the same mobility as untreated undecaprenol. To characterize further the lipid moiety of the glucophospholipid, a polyisoprenol was purified from the neutral lipid of S. sanguis. The polyisoprenol was converted in the presence of ATP, UDP-glucose, and the particulate enzyme into a lipid which exhibited the same thin-layer chromatographic mobility as the glucophospholipid. The structure of the polyisoprenol was determined by nuclear magnetic resonance and mass spectrometry to be an undecaprenol with an internal cis-trans ratio of 7:2. These results indicate that the glucophospholipid is glucosyl monophosphoryl undecaprenol. The glucosyl moiety of the glucophospholipid was shown to be incorporated in the presence of the particulate enzyme into a macromolecule which was characterized as a lipoteichoic acid by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and DEAE-cellulose column chromatography. This result indicates that glucosyl monophosphoryl undecaprenol is the direct glucosyl donor in the synthesis of lipoteichoic acid.

Antigens of Streptococcus sanguis: purification and characterization of the b antigen

The antigen defining Streptococcus sanguis serotype 2 has been designated the b antigen. This antigen can be detected in extracts, obtained from whole cells by autoclaving (Rantz and Randall extraction), as a single precipitin band using a reference antiserum (M-5). However, the extract can also be shown to contain a teichoic acid using anti-polyglycerol phosphate serum. This teichoic acid does not contain the antigenic determinant for group H specificity. Studies of the b antigen have been hampered because of the difficulty in separating the b antigen from the teichoic acid using ion-exchange and molecular sieve chromatography. However, a relatively pure preparation has been obtained by affinity chromatography using anti-polyglycerol phosphate serum coupled to Sepharose. The isolated b antigen is a typical streptococcal cell wall polysaccharide composed of glucose, rhamnose, and N-acetylglucosamine in a molar ratio of 2.5:1.0:0.1. The antigen appears to have a single antigenic determinant closely related to isomaltose (glucose alpha-1,6-glucoside) based upon hapten inhibition studies.

Biosynthesis of oligosaccharide-lipid in Streptococcus sanguis

An oligosaccharide-lipid containing N-acetyl d-glucosamine (GlcNAc), l-rhamnose, and d-glucose was synthesized when the particulate enzyme from Streptococcus sanguis was incubated with UDP-GlcNAc, TDP-rhamnose, and UDP-glucose. The incorporation of d-glucose into the lipid was dependent on the preincorporation of l-rhamnose, which in turn was dependent on that of GlcNAc. This indicates that the order of sugar incorporation is GlcNAc, l-rhamnose, and d-glucose. The synthesis of GlcNAc-lipid was stimulated twofold by ATP and was inhibited strongly by UDP and slightly by UMP, CDP, and TDP, but not by all other nucleoside diphosphates and nucleoside monophosphates tested. A [gamma-(32)P]ATP labeling experiment indicated that some acceptor lipid was present in nonphosphorylated form. The acid and alkaline stabilities of the GlcNAc-lipid were similar to those of glycosyl undecaprenylphosphate, and the thin-layer chromatographic mobility of the lipid was slightly faster than that of the mannosylphosphorylundecaprenol. The molar ratio of phosphate to GlcNAc in purified GlcNAc-lipid was found to be 0.96:1. These results suggested that the GlcNAc was attached to the lipid moiety, presumably undecaprenol, by phosphodiester bonds. The incorporation of l-rhamnose into the lipid was inhibited by UDP and UMP, respectively, in a manner similar to the incorporation of GlcNAc. This suggested that the oligosaccharide was also linked to the lipid moiety by phosphodiester bonds.

Characterization of group H streptococcal temperate bacteriophage phi 227

phi 227, a temperate phage from a group H streptococcus (Streptococcus sanguis), was propagated vegetatively in group H strain Wicky 4-EryR, and its characteristics were determined. A procedure dependent on multiplicity of infection, incubation time, and treatment of crude lysates with diatomaceous earth was found to optimize phage yield, resulting in titers of 1 X 10(10) to 2 X 10(10) PFU/ml. Without prior treatment with diatomaceous earth, subsequent purification procedures (methanol, ammonium sulfate, polyethylene glycol) gave recoveries of less than 1% of crude lysate titers. Adsorption of phi227 to host cells was relatively unaffected by the medium, but calcium (not substituted by magnesium) was required for formation of infectious centers. The phage receptor was present on purified cell walls, resisted trypsin and heat, and was removed ty hydrochloric acid, trichloracetic acid, and hot formamide: however, formamide-extracted material failed to inactivate phage, and the nature of the receptor is unknown. Single-step growth experiments showed a latent period of 39 min and a burst size of 100 PFU/infectious center; results were unaffected by omission of supplemental Ca2+, by supplementation with Mg2, addition of glucose, or changes of pH between 6.35 and 8.0; but increased temperature (40 to 43 degrees C) shortened the latent period and decreased the burst size. The latent period was prolonged in genetically competent host cells and in chemically defined medium; and in the latter, the burst size was smaller. Phage replication was sensitive to those metabolic inhibitors which inhibited the host streptococcus: these included rifampin, fluorodeoxyuridine, hydroxyurea, dihydrostreptomycin, and 6-P-hydroxyphenylazouracil. The data suggest that phi227 does not code for a rifampin-resistant RNA polymerase. However, in a rifampin-resistant host strain, phage replication and lysogen formation were both decreased suggesting that altered host core polymerase had less affinity for (some) promotors on the phi227 template. In transfection, a Ca2+-dependent stabilization step that was inhibited by Mg2+ was demonstrated; transformation was not affected by either Ca2+ or Mg2+, and the site and nature of the stabilization are unknown. More than one molecule of DNA was required for plaque formation. Biophysical characterization showed a type B phage of buoyant density (CsCl) 1.50, containing five proteins and 54.8% DNA. The duplex linear DNA had a molecular weight (calculated from contour length) of 23.2 X 10(6) and a guanine plus cytosine content (calculated from melting point) of 42.3 mol%. Similar characterizations of streptococcal phages, including biophysical data, have not been previously available.