Lipoteichoic Acid Synthesis Research Articles

Effects of penicillin on synthesis and excretion of lipid and lipoteichoic acid from Streptococcus mutans BHT.

Cultures of Streptococcus mutans BHT grown for at least eight generations in a chemically defined medium containing [1(3)-14C]glycerol, when treated with growth-inhibitory concentrations (0.2 micrograms/ml) of benzylpenicillin (Pen G), produced and excreted increased amounts of lipid and lipoteichoic acid per unit of cells. Cellular lysis was not observed. Compared with untreated controls, lipid excretion increased 15-fold, and lipoteichoic acid excretion increased 6-fold, 4 h after the addition of Pen G. All lipid species showed increased synthesis and excretion after exposure to Pen G. Although the same lipid types were found in both the Pen G-treated and the untreated cultures, the percent composition was altered after treatment with Pen G. The most dramatic example of this was the percentage of intracellular diphosphatidylglycerol found in the Pen G-treated cultures, 22.6%, in contrast to 5.3% found in the untreated cultures.

Surface components in adhesion of group a streptococci to pharyngeal epithelial cells

The role of different cell surface components in the adhesion ofStreptococcus pyogenes to pharyngeal cells was investigated. No difference between parental strains and Mnegative mutants in adhesiveness was detected. Purified lipoteichoic acid markedly inhibited adhesion of group A streptococci. A similar inhibitory effect was observed with group B streptococci andStaphylococcus, aureus strains. All the A-variant streptococci tested demonstrated decreased adhesion ability. In particular, the A-486 strain, with a temperaturedependent variation in the synthesis of the group-specific carbohydrate, adhered less when cultured at nonpermissive temperature (38°C). No effect of growth temperature on lipoteichoic acid synthesis was detected. Preincubation of epithelial cells with group-A-specific polysaccharide greatly decreased the number of bacteria per cell that adhered. These results suggest that C polysaccharide might be specifically involved in the adhesion of group A streptococci.

Morphological effect of cerulenin treatment on Streptococcus faecalis as studied by ultrastructure reconstruction.

Exponential-phase cells of Streptococcus faecalis ATCC 9790 were treated with a concentration of cerulenin (5 micrograms/ml) that has been shown to block both lipoteichoic acid and lipid synthesis and cell division within 10 min. The morphological effect of this treatment was studied by making three-dimensional reconstructions of cells based on measurements taken from axial thin sections. This analysis indicated that cerulenin interferes with cell division by inhibiting normal constriction of the division furrow and centripetal growth of the cross wall in envelope growth sites. Rather than dividing, many of the sites in treated cells apparently continue to elongate and produce abnormally large amounts of peripheral wall surface. These observations were interpreted in terms of a previously proposed model in which cerulenin would prevent the synthesis of a lipid-containing inhibitor of autolytic enzyme activity needed for division. In addition, measurements showed that the average number of envelope growth sites per cell increased during treatment, suggesting that although cerulenin treatment blocks division, it does not interfere with the formation of new envelope growth sites. It was also observed that the size and frequency of mesosomes did not decline during the 60-min period of drug treatment. This tends to decrease the likelihood that mesosomes are formed from a pool of intracellular membrane precursors that would be depleted during a period of restricted lipid biosynthesis.

The biosynthesis of nascent membrane lipoteichoic acid of Streptococcus faecium (S. faecalis ATCC 9790) from phosphatidylkojibiosyl diacylglycerol and phosphatidylglycerol.

Phosphatidylkojibiosyl diacylglycerol functions as the acceptor of sn-glycerol 1-phosphate moieties from phosphatidylglycerol in the in vitro synthesis of the membrane lipoteichoic acid of Streptococcus faecium (S. faecalis ATCC 9790). The enzyme catalyzing this polymer-forming reaction is membrane-bound. The majority of the product is water-soluble, is excluded from Sepharose 6B, and, after longer incubations, changes to a form that co-precipitates with protein upon exposure to a denaturing agent. These properties are shared by the polyglycerol phosphate-containing membrane lipoteichoic acid isolated from whole cells of S. faecium. However, unlike the lipoteichoic acid generated in vivo, the glycerol phosphate polymer portion of the product synthesized in vitro is not substituted and, therefore, is considered a nascent lipoteichoic acid intermediate.

Effect of 3,4-dihydroxybutyl-1-phosphonate on phosphoglyceride and lipoteichoic acid synthesis in Bacillus subtilis.

3,4-Dihydroxybutyl-1-phosphonate (CH2OHCHOHCH2CH2PO3HPO3H2), an analogue of glycerol 3-phosphate, preferentially inhibits the rate of synthesis and accumulation of phosphatidylglycerol in Bacillus subtilis W23 and 168. The rate of phosphatidylethanolamine synthesis is only slightly inhibited, whereas that of lysylphosphatidylglycerol is somewhat stimulated. As expected, decreased phosphatidylglycerol synthesis results in the inhibition of the formation of the putative lipoteichoic acid precursor, sn-glycero-1-phospho-beta-gentiobiosyldiacyglycerol and of lipoteichoic acid itself.

Effect of cerulenin on Streptococcus faecalis macromolecular synthesis and cell division

The antibiotic cerulenin has been used to study macromolecular synthesis and cell division in Streptococcus faecalis. The data suggest that lipid and lipoteichoic acid synthesis as well as cell number increase are affected prior to any observable effects on overall mass increase or DNA, RNA, protein, or peptidoglycan synthesis. Treatment with cerulenin of cultures growing at various rates and analysis of the subsequent cell divisions indicate that the antibiotic may block a cell cycle event that precedes the completion of chromosome replication by about 10 min.