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S Razin

Publications and source records attributed to S Razin.

At least 55 records · Page 3Linked to original sources
PubMed1983

DNA cleavage patterns as indicators of genotypic heterogeneity among strains of Acholeplasma and Mycoplasma species.

Electrophoretic patterns of digestion products of Acholeplasma and Mycoplasma DNA by restriction endonucleases were compared. The patterns of Acholeplasma axanthum strains isolated from a variety of hosts and habitats differed markedly from each other, indicating considerable genotypic heterogeneity among strains included in this species. Heterogeneity was less marked among the Acholeplasma oculi strains tested, and was minimal among strains of the avian pathogen Mycoplasma gallisepticum. Strains of Mycoplasma genitalium isolated from the urethra of patients with non-gonococcal urethritis and from the urethra of an experimentally infected chimpanzee yielded identical cleavage patterns, indicating a high degree of genetic homogeneity of these strains. The data support the notion that mycoplasma species of strict host and tissue specificity exhibit marked genetic homogeneity. The advantages and deficiencies of the use of DNA cleavage patterns for classification purposes are discussed.

Acholeplasma↗
PubMed1982

Preferential uptake of lipids by mycoplasma membranes from human plasma low-density lipoproteins.

The binding and transfer of low-density lipoprotein (LDL) constituents to mycoplasma membranes were examined. Mycoplasma capricolum was found to bind more 125I-labeled LDL than Acholeplasma laidlawii. Free and esterified cholesterol uptake was 3-4 times higher in M. capricolum than in A. laidlawii. Cholesterol transfer to the membranes of both organisms far exceeded the amounts of cholesterol expected according to LDL protein found associated with the membranes. Trypsin digestion of the membranes prior to incubation with LDL decreased the binding of LDL and the transfer of free cholesterol to M. capricolum membranes but did not affect these processes with A. laidlawii membranes. These findings suggest the existence of protease-sensitive receptors on M. capricolum cell surface responsible for tighter contact with LDL. Analysis of LDL after incubation with large amounts of M. capricolum membranes revealed a loss of 60% of the lipoprotein-free cholesterol, 25.9% of the esterified cholesterol, and 20.7% of phospholipids without appreciable loss of protein. Rate zonal ultracentrifugation showed that the LDL separated as a single symmetrical peak, denser than the control. Electron microscopy showed that the lipoprotein particles retained their spherical shape but became about 10% smaller in diameter. These observations lead us to conclude that both free and esterified cholesterols are transferable from LDL to the membranes by a simple exchange process which does not involve prolonged contact or fusion of the particle with the membrane and does not result in degradation of the lipoprotein particle. We propose that similar mechanisms of free and esterified cholesterol transfer may also operate in vivo and contribute to the process of cholesterol exit from the plasma.

Acholeplasma laidlawii↗
PubMed1982

Ribosomal RNA genes in Mycoplasma.

Using Southern blotting analysis with labelled mycoplasmal ribosomal RNA as probe, two fragments (1 Kb and 5 Kb) were detected in an EcoR I digest of Mycoplasma capricolum DNA. This analysis revealed that the 5 Kb fragment carries both 16S rRNA sequences and the entire 23S rRNA gene of this mycoplasma. The 1 Kb fragment contains 16S rRNA sequences only. The 5 Kb EcoR I fragment has been cloned and used to characterize the structure of rRNA cistrons in various Mycoplasma strains. These experiments clearly demonstrate a substantial homology of Mycoplasma capricolum rRNA sequences with the E. coli rRNA cistron on one hand, and with Mycoplasma mycoides subsp. capri and Acholeplasma laidlawii on the other hand. This analysis also reveals two rRNA cistrons in Mycoplasma mycoides subsp. capri and Acholeplasma laidlawii whereas one rRNA cistron is present in Mycoplasma capricolum.

Acholeplasma laidlawii↗
PubMed1982

Effects of ionophores and dicyclohexylcarbodiimide on Mycoplasma gallisepticum adherence to erythrocytes.

To test the influence of the electrochemical ion gradient across mycoplasma membranes on the capacity of organisms to adhere to host cells, Mycoplasma gallisepticum cells were treated with valinomycin, carbonylcyanide m-chlorophenylhydrazone, and N,N'-dicyclohexylcarbodiimide (DCCD) singly or in combination. Uptake of [3H]tetraphenylphosphonium by the treated cells was employed as a measure of the effects of the ionophores on membrane potential. In the absence of K+, valinomycin increased, whereas carbonylcyanide m-chlorophenylhydrazone, and DCCD decreased [3H]tetraphenylphosphonium uptake. However, with a high level of K+ or with DCCD, uptake of [3H]tetraphenylphosphonium in the presence of valinomycin decreased below control levels, indicating that, generally, the ionophores affected membrane potential in the expected manner. The treated organisms were tested for their capacity to attach to glutaraldehyde-fixed human erythrocytes. DCCD was the best inhibitor of mycoplasma attachment, and in combination with valinomycin attachment, capacity decreased by about 40%. The combination of valinomycin plus carbonylcyanide m-chlorophenylhydrazone was less effective; it decreased attachment by about 15 to 25%. It was concluded that the dissipation of ion gradients across cell membranes decreases only partially mycoplasma adherence, in line with previous findings that isolated mycoplasma membranes retain the major part of the attachment capacity of intact cells.

Adhesiveness↗
PubMed1982

Genomic and phenotypic analyses of Mycoplasma pneumoniae strains.

Mycoplasma pneumoniae strains PI-1428, M129, B176, FH, and MAC were analyzed for homology by DNA-DNA hybridization, thermal elution midpoints of the DNA-DNA heteroduplexes, DNA cleavage patterns with restriction endonucleases, and protein gel electrophoretic profiles. These properties were compared with biological assays, such as antigenic reactivity with reference antisera in the growth inhibition and metabolic inhibition tests, as well as the ability to attach to human WiDr cell cultures. The avirulent, nonhemadsorbing strain B176 could be differentiated from the others by diminished attachment capacity to WiDr cells and by slightly reduced DNA homology. The other strains appeared to be identical when examined by these procedures. No significant differences were detected among any of the strains by the metabolic inhibition or growth inhibition tests. The DNA cleavage patterns of the five strains were also similar, although strains FH and MAC differed from the other three strains in a few bands. These results demonstrate that these five strains are similar and that the species M. pneumoniae is remarkably homogeneous.

Adhesiveness↗
PubMed1981

Stable RNA synthesis and its control in Mycoplasma capricolum.

The synthesis of stable RNA in Mycoplasma capricolum was studied by [32P] labeling of cellular RNA of cells grown in a partially-defined medium in the presence or absence of an amino acid mixture supplement. The results indicate that M. capricolum employs the same stringent control mechanism used by E. coli cells, as judged by a decreased synthesis of stable RNA and accumulation of 5'-triphosphoguanosine-3'-diphosphate (pppGpp) and 5'-diphosphoguanosine-3'-diphosphate (ppGpp) in response to amino acid starvation. In addition, the results suggest that precursors of stable RNA accumulate and an intracellular pool of the precursors exists at all times under the growth conditions used by us. These findings may be interpreted to reflect a slow rate of RNA processing in M. capricolum.

Amino Acids↗
PubMed1981

Lipid and protein membrane components associated with cholesterol uptake by Mycoplasmas.

Membranes of Mycoplasma species take up 2--4 times more exogenous cholesterol than membranes of Acholeplasma species. To test whether the lower cholesterol uptake capacity of Acholeplasma is due to the high glycolipid content of their membranes, the phospholipids of Acholeplasma laidlawii and Mycoplasma capricolum membranes were hydrolyzed by phospholipase A2. Digestion removed about 30% of the polar lipids of A. laidlawii, leaving the glycolipids and phospholglycolipids intact, and about 70% of the polar lipids of M. capricolum, the residue consisting mostly of sphingomyelin. Cholesterol uptake by the treated membranes from phosphatidylcholine/cholesterol vesicles decreased in rough proportion to the amount of polar lipid removed, indicating that the glycolipids in A. laidlawii membranes can participate in cholesterol uptake. Trypsin digestion of growing cells and isolated membranes of M. capricolum decreased cholesterol uptake by about one-half. Similar treatment of A. laidlawii cells and membranes had no effect on cholesterol uptake. These findings suggest the existence of protease-sensitive receptors on the cell surface of M. capricolum responsible for tighter contact with the cholesterol/phosphatidylcholine vesicles. It is proposed that the ability of Mycoplasma species to take up large quantities of exogenous cholesterol and phospholipids depends on the presence of protein receptors for cholesterol donors, receptors which are absent in Acholeplasma species.

Acholeplasma laidlawii↗
PubMed1981

Adhesion of mycoplasmas to eukaryotic cells.

Many pathogenic mycoplasmas are surface parasites, adhering to the epithelial linings of the respiratory and urogenital tracts. Since mycoplasmas lack cell walls their plasma membrane comes in close contact with that of their host, allowing exchange of components between the two membranes and possibly fusion. The tight association of the parasite with its host is illustrated in scanning electron micrographs of Mycoplasma pneumoniae and M. gallisepticum adhering to human red blood cells. Specialized structure at the tips of the mycoplasma cells appear to function as attachment organelles. Our main aim has been to chemically define the receptors on the host cell and the binding sites on the mycoplasma cells responsible for adhesion. Glycophorin (the major sialoglycoprotein of human red blood cells) serves as the main or sole receptor for M. gallisepticum whereas M. pneumoniae binds to additional receptors on human red blood cells. Trypsin treatment of M. pneumoniae cells abolishes their ability to attach to human red cells, suggesting the protein nature of the binding sites. M. pneumoniae membranes solubilized by detergents were subjected to affinity chromatography on glycophorin-Sepharose so that membrane components with high affinity for glycophorin could be isolated. The fraction isolated consisted of several proteins (relative molecular mass 25 000 and 45 000). The binding of this fraction to red cells was relatively low but appeared to be specific, as it was inhibited by glycophorin but not by its hydrophobic moiety. The possibility is discussed that the exposure of the binding sites on the mycoplasma cell surface is influenced by the electrochemical ion gradient across the membrane.

Adhesiveness↗
PubMed1981

Role of energy metabolism in Mycoplasma pneumoniae attachment to glass surfaces.

Attachment values of Mycoplasma pneumoniae to glass are normally very low when tested in buffer containing bovine serum albumin (10 mg/ml). However, the addition of one of the metabolizable sugars glucose, fructose, or mannose increased attachment more than 10-fold. The effect was dose dependent with a distinct optimum at about 0.25 mg/ml. Higher concentrations reduced this effect. Not only the sugars themselves but also the products of their catabolism, pyruvate and phosphoenolpyruvate, enhanced attachment. Pyruvate was effective in the same range of concentrations as the sugars, whereas phosphoenolpyruvate enhanced attachment at a significantly lower concentration (0.001 mg/ml). Higher levels of these substances also resulted in a decrease of attachment. The glucose-induced increase could be partially inhibited by glucose analogs, especially by 3-O-methyl-glucopyranoside, and by various inhibitors or glycolysis. Furthermore, attachment was strongly reduced by the uncoupling agents carbonylcyanide m-chlorophenylhydrazone and 2,4-dinitrophenol, as well as by dicyclohexylcarbodiimide, an inhibitor of the membrane-bound Mg2+-adenosine triphosphatase, whereas the ionophore valinomycin increased attachment by about 30%. These findings provide strong evidence for coupling between the attachment process of M. pneumoniae to glass and the utilization of metabolic energy.

Chloramphenicol↗
PubMed1981

Attachment of killed Mycoplasma gallisepticum cells and membranes to erythrocytes.

To correlate viability with attachment capacity, Mycoplasma gallisepticum cell harvested at different growth phases and treated by various agents were tested for their capacity to attach to human erythrocytes. The results show that viability per se is not essential for M. gallisepticum attachment to erythrocytes, as cells killed by ultraviolet irradiation anmd membranes isolated by lysing M. gallisepticum cells by various means retained attachment capacity. However, treatment of the mycoplasmas by protein-denaturing agents, such as heart, glutaraldehyde, or prolonged exposure to low pH, drastically affected or even abolished attachment, supporting the protein nature of the mycoplasma membrane components responsible for specific binding to the sialoglycoprotein receptors on the erythrocytes.

Adhesiveness↗
PubMed1980

Phospholipid and cholesterol uptake by Mycoplasma cells and membranes.

The ability of growing mycoplasma cells and their isolated membranes to take up exogenous phospholipids was correlated with their ability to take up cholesterol. Horse serum or vesicles made of phosphatidylcholine and cholesterol served as lipid donors. Growing cells of five Mycoplasma species took up significant quantities of phosphatidylcholine and sphingomyelin as well as free and esterified cholesterol. In contrast, growing cells of three Acholeplasma species failed to take up any of the exogenous phospholipids, and only incorporated low amounts of free cholesterol and no esterified cholesterol. Hence, the ability of mycoplasmas to take up large quantities of cholesterol appears to be correlated with an ability to take up exogenous phospholipids. Isolated membranes of Mycoplasma capricolum and Acholeplasma laidlawii took up lower amounts of cholesterol than did membranes of growing cells and did not take up phospholipids. Inhibition of M. capricolum growth decreased the ability of the cells to take up exogenous phospholipids and cholesterol. The possibility that the contact between the lipid donors and the membrane involves specific receptors best exposed in actively growing cells is discussed.

Acholeplasma↗
PubMed1980

Methylated bases in mycoplasmal DNA.

The DNAs of four Mycoplasma and one Acholeplasma species were found to contain methylated bases. All of the five species contained 6-methyladenine (m6Ade), the methylated base characteristic of prokaryotic DNA. The extent of methylation of adenine residues in the mycoplasmal DNA ranged from 0.2% in Mycoplasma capricolum to about 2% in Mycoplasma arginini and Mycoplasma hyorhinis with intermediate methylation values for Mycoplasma orale and Acholeplasma laidlawii DNAs. About 5.8% of the cytosine residues in M. hyorhinis DNA were methylated also. Analysis of cell culture DNA for the presence of m6Ade as a means for detection of contamination by mycoplasmas, and the phylogenetic implications of the finding of methylated bases in mycoplasmal DNAs are discussed.

5-Methylcytosine↗
PubMed1980

Scanning electron microscopy of mycoplasmas adhering to erythrocytes.

The interaction of Mycoplasma pneumoniae and Mycoplasma gallisepticum with human erythrocytes (RBC) was studied by scanning electron microscopy. The tight nature of the attachment of the microorganisms to the RBC was indicated by the indentation of the RBC surface at the site of attachment of M. gallisepticum cells and by traction and resulting distortion in the shape of the RBC at the point of its attachment to M. pneumoniae filaments growing on glass or plastic. In many cases attachment took place via the tip of the filaments, the membrane of the parasite appearing to be fused with that of the RBC. The morphology of the mycoplasmas growing on cover slips conformed in general with previous descriptions obtained by scanning electron microscopy. Growth of M. pneumoniae on glass or plastic consisted of branching filaments spread on the inert surface and microcolonies made up of intertwining filaments projecting into the medium. The filaments had a bulbous swelling adjacent to a tapered tip end. A few filaments were shown to have a ropelike helical twist. M. gallisepticum grown on the cover slips of Leighton tubes had a peculiar fusiform or teardrop shape with blebs at one or both poles of the cells. Elongated filamentous forms and chains of coccobacillary bodies were observed as well.

Cell Adhesion↗
PubMed1980

Isolation of binding sites to glycophorin from Mycoplasma pneumoniae membranes.

Sialoglycoproteins are major receptor sites for attachment of Mycoplasma pneumoniae to respiratory epithelium and erythrocytes (RBC). We used glycophorin, the major sialoglycoprotein of human RBC, as a ligand in affinity chromatography for the isolation of the binding sites from M. pneumoniae membranes. Membranes isolated from M. pneumoniae cells, radioiodinated by the lactoperoxidase technique, were treated with 0.5% deoxycholate. The insoluble residue, exhibiting an increased capacity to bind to RBC, was solubilized by 0.1% sodium dodecyl sulfate. The solubilized material was subjected to chromatography on a glycophorin-Sepharose column. The fraction retained on the column was eluted with 0.2% sodium dodecyl sulfate. It lacked the high-molecular-weight polypeptides and was highly enriched with two polypeptides (apparent molecular weights, 45,000 and 25,000). The eluted fraction exhibited a high capacity to bind to glycophorin-Sepharose beads and a lower capacity to bind to RBC. The binding of the eluted fraction to RBC was almost completely abolished by glycophorin, but not by its hydrophobic moiety. Binding of the fraction to glycophorin-Sepharose beads was inhibited to about the same extent by both glycophorin and its hydrophobic moiety, suggesting that components of the eluted fraction are also capable of binding to the hydrophobic moiety of glycophorin, which is apparently exposed on the beads but not on the RBC surface.

Binding Sites↗
PubMed1979

Is the vertical disposition of Mycoplasma membrane proteins affected by membrane fluidity?

The influence of the physical state of the membrane lipid matrix on the vertical disposition of membrane proteins was studied with Acholeplasma laidlawii. Changes in membrane fluidity were brought about by altering the fatty acid composition of membrane lipids, by changing the growth temperature, by aging of cultures and by inducing changes in the membrane lipid-to-protein ratio through treatment with chloramphenicol. The lactoperoxidase-mediated iodination technique was used to label membrane proteins exposed to the aqueous surroundings. The degree of exposure of the iodine-binding sites of membrane proteins on the external surface of intact cells was found to undergo significant changes on varying growth conditions, but the changes could not be consistently correlated with changes in membrane fluidity, nor were they discernible on iodination of isolated membranes.

Acetates↗
PubMed1979

Adherence of Mycoplasma gallisepticum to glass.

Attachment of washed Mycoplasma gallisepticum cells to glass was quantified with organisms in which membrane lipids were labelled with 3H. Siliconization of the test tubes decreased attachment, while centrifugation increased it. Attachment increased with temperature, decreased with increasing pH and ionic strength of the attachment mixture, but was unaffected by Ca2+, Mg2+ and EDTA. This suggests that ionic bonds, but not salt bridges, participate in the attachment process. Glycophorin, the major receptor responsible for M. gallisepticum attachment to erythrocytes, partially inhibited the attachment of the organisms to glass. However, bovine serum albumin also decreased attachment. Extensive pretreatment of the organisms with trypsin decreased their ability to attach to glass by about 35 to 40%. Trypsin and pronase failed to detach the organisms already bound to glass, suggesting that external mycoplasma cell components, other than membrane proteins, also participate in attachment of the organisms to glass.

Cell Count↗