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Biomedical subjects

M Sarvas

Publications and source records attributed to M Sarvas.

87 records · Page 5Linked to original sources
PubMed1976

T2 lipopolysaccharide antigen of Salmonella: comparison of the properties of T2 and mucoid forms.

The T2 form of Salmonella was found to resemble mucoid mutants to some extent by growing as rather slimy colonies, especially at low temperatures. Its sensitivity to rough-specific phages was greatly reduced at low temperature. However, the T2 form did not produce colanic acid. The mucoid mutants of Salmonella studies corresponded to previously described mucoid mutants of Escherichia coli culturally, chemically,and genetically.

Escherichia coli↗
PubMed1976

Bacteriophage-resistant mutants of Salmonella typhimurium deficient in two major outer membrane proteins.

Mutants resistant to bacteriophages (P221 and PH105 or PH51) were isolated from a rfa strain of Salmonella typhimurium. They were found deficient in separate 33,000- to 36,000-dalton band proteins (major band proteins). Double mutants derived from both types of mutants were deficient in both of the bands. The growth behavior of all the mutants was normal. The outer membrane of the mutants appeared to be more wrinkled than normal and formed vesicles in many of the mutants. In freeze-fractured cells, changes were seen in the outer membrane (particleless patches in the concave fracture face, the particles themselves being smaller than normal). These changes were more marked in the double mutants.

Adsorption↗
PubMed1976

Effect of polymyxin on the ultrastructure of the outer membrane of wild-type and polymyxin-resistant strain of Salmonella.

The effect of polymyxin on two sets of Salmonella mutants was studied by thin-section and scanning electron microscopy. Polymyxin (in increasing concentrations, starting just below bactericidal effect) caused the appearance of the previously described rodlike projections on the cell surface of wild-type (smooth, polymyxin-sensitive) bacteria. These projections seemed to involve the outer membrane of the cell wall. In rough mutants, which are deficient in lipopolysaccharide, the projections were much smaller and flat. Higher concentrations of polymyxin were required to produce morphological effects in polyxmin-resistant mutants of both smooth and rough forms. Furthermore, in these mutants polymyxin caused vesicle-like bulging of the total outer membrane quite different in appearance from the rodlike projections of the wild type.

Cell Membrane↗
PubMed1973

Mitogenic effect by lipopolysaccharide and pokeweed lectin on density-inhibited chick embryo fibroblasts.

The B lymphocyte mitogens, bacterial lipopolysaccharide (LPS), pokeweed lectin, and tuberculin, induced proliferation in density-inhibited monolayer cultures of chick embryo fibroblasts. The stimulation was seen both as an early increase in sugar uptake and cell volume and later as an increase in thymidine incorporation and cell number. The concentration of LPS maximally stimulating fibroblasts was remarkably low, about 0.1-1 ng/ml. LPS preparation with very different sugar chains gave quite similar results indicating that the architecture of the hydrophilic carbohydrate part is not critical for the mitogenic effect.

Animals↗
PubMed1971

Mutant of Escherichia coli K-12 defective in D-glucosamine biosynthesis.

A mutant was isolated from a derivative of Escherichia coli K-12 after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. This mutant contained normal levels of 2-amino-2-deoxy-d-glucose-6-phosphate ketol-isomerase (deaminating) (EC 5.3.1.10), but no detectable activity of l-glutamine:d-fructose-6-phosphate amino-transferase (EC 2.6.1.16). It required either N-acetyl-d-glucosamine or d-glucosamine for growth, and went into rapid lysis when the supply of these compounds was exhausted. In medium containing 11% sucrose, the cells were converted into spheroplasts in the absence of d-glucosamine.

Cell Wall↗
PubMed1971

Biosynthesis of T1 antigen in Salmonella: origin of D-galactofuranose and D-ribofuranose residues.

The "T1 side chain" portion of cell wall lipopolysaccharide from T1 strains of Salmonella contains d-galactofuranose and d-ribofuranose residues. Isotope labeling studies, using intact cells of mutants each blocked at either of the two different steps of d-galactose metabolism (uridine diphosphate-glucose 4-epimerase and galactose-1-P uridylyl transferase) or at phosphoglucoisomerase, led to the following conclusions. (i) d-Galactofuranose residues are synthesized from d-galactopyranose or its derivatives, rather than by a direct conversion from other hexopyranoses or their derivatives. (ii) The pyranose-to-furanose conversion does not appear to take place at the level of the free d-galactose or d-galactose 1-phosphate. This result suggests that the conversion may occur at the stage of uridine diphosphate-d-galactose. (iii) In a mutant lacking phosphoglucoisomerase, d-ribofuranose residues in T1 side chains contained (14)C derived from exogenous d-fructose-U-(14)C, but little (3)H from exogenous d-glucose-1-(3)H. Thus, no evidence was found for a direct pathway of aldohexose-to-ribose conversion involving a loss of one of the carbons in the C2-C6 moiety of aldohexoses. This suggests, but does not prove, that the T1 ribofuranose residues are synthesized by conventional mechanisms involving hexose monophosphate shunt and transketolase-transaldolase reactions.

Antigens↗
PubMed1971

Biosynthesis of T1 antigen in Salmonella: biosynthesis in a cell-free system.

A particulate fraction from a T1 form of Salmonella typhimurium incorporated radioactivity from uridine diphosphate (UDP)-(14)C-glucose into products associated with the particulate enzyme. A major fraction of the incorporated radioactivity was found in the cell wall lipopolysaccharide fraction. Acid hydrolysis of incorporation products produced labeled galactose, ribose, and also glucose. The incorporation of glucose could be dissociated from the incorporation of galactose and ribose under certain conditions, and was assumed to represent incorporation into a polymer not related to T1 antigen. The incorporation of galactose and ribose probably represented the synthesis of T1 side chains of lipopolysaccharide, because (i) particulate fractions from non-T1 strains incorporated much less of these sugars and (ii) periodate oxidation and borohydride reduction converted a large portion of incorporated galactose residues into arabinose. The latter finding indicates that the galactose residues are galactofuranosides substituted either at C2 or C3; about 70% of the galactose residues in T1 side chains are known to be galactofuranosides substituted at C3. UDP-(14)C-galactose preparation used was not contaminated by UDP-(14)C-galactofuranose; therefore pyranose-to-furanose conversion must have taken place at some step during the reactions described above. The mechanism of conversion of galactose to ribose is not clear, but it was not found to involve a selective elimination of C1 or C6 of galactose or glucose.

Antigens↗
PubMed1970

Bacteriophage attachment to the somatic antigen of salmonella: effect of o-specific structures in leaky R mutants and s, t1 hybrids.

The phage adsorption ability and serological specificity of different Salmonella strains having either complete or leaky mutations in their lipopolysaccharide (LPS) synthesis were compared, together with their genotype and sugar composition, to provide a set of standards relating these parameters to LPS structure. Strains that had T1-specific side chains in their LPS, both with or without O side chains, were examined to learn more about the organization of these two side chains in the LPS and a possible competition between them. It was found that (i) adsorption of O-specific antibodies was a very sensitive test for the presence of even very small amounts of O-specific structures, (ii) that phage P22 adsorption was dependent on the presence of a nearly complete O side chain complement, and both long and numerous O side chains were required, and (iii) that the adsorption of the phages FO (Felix O-1), 6SR, and Br2, which attach to structures in the LPS core, was a sensitive indicator of any defect in O-antigen synthesis, and well developed O side chains blocked their attachment efficiently. Semirough (SR) strains with only one O-specific repeating unit per side chain adsorbed FO efficiently, whereas the access of the 6SR and Br2 phages to their receptors was blocked. Strains with T1 side chains adsorbed the FO and 6SR phages efficiently, whereas the adsorption of the Br2 phage was blocked to a large extent. The phage adsorption of four S, T1 strains (with both O and T1 side chains) showed that, as the amount of O side chain material increased, there was a reduction of the adsorption of phages in the following order: 6SR, Br2, and FO. P22 attachment appeared with the increase of O side chains. The LPS composition of these strains revealed a 10-fold reduction of the O-specific structures compared to the smooth parent strain, whereas the amount of T1-specific material was the same as in T1 strains. The short O side chains of a SR, T1 strain were, however, not reduced in number, suggesting that the apparent competition between O and T1 side chains may not be a competition for available sites in the LPS.

Journal Article↗