Summary: Formation of iodophilic polysaccharide (IPS) from glucose was demonstrated in 27 strains of Bacteroides fragilis. Synthesis was dependent on the glucose concentration of the medium, the pH and the growth phase. When glucose was in short supply the cellular polysaccharide was degraded rapidly at pH 4.5 to 6.5 and fatty acids accumulated in the medium. Storage of IPS was not responsible for the low carbon recoveries observed in fermentation balance studies. In electron micrographs of thin sections, the IPS was observed as cytoplasmic granules dispersed throughout the whole cell. After extraction and purification the IPS was characterized as a glycogen.
Summary: Mutants of Streptomyces parvulus that are blocked in the synthesis of the phenoxazinone-containing antibiotic, actinomycin, were isolated by the ‘agar piece’ method (after ultra-violet irradiation or treatment with 8-methoxypsoralen plus near-ultraviolet light). Radio-labelling experiments in conjunction with paper, thin-layer and column chromatography revealed that 4-methyl-3-hydroxyanthranilic acid (MHA) is a major metabolite accumulated by these mutants. Studies in vitro and in vivo provided evidence that MHA is a precursor of the phenoxazinone chromophore, actinocin. Normally MHA does not accumulate during growth or antibiotic synthesis by the parental strains. Protoplasts derived from the mutant strain AM5 synthesized MHA in significant amounts. A scheme is proposed for the biosynthesis of actinomycin D that accounts for the accumulation of MHA by the mutants.
Summary: A bacterium capable of growth on 5-hydroxyisophthalate was isolated from soil. Both 4,5-dihydroxyisophthalate and protocatechuate were found in the growth medium and were also oxidized by bacterial extracts. These extracts catalysed the decarboxylation of 4,5-dihydroxyisophthalate to give protocatechuate under anaerobic conditions. Extracts oxidized 5-hydroxyisophthalate only when reduced pyridine nucleotide was present, and did so at a faster rate with NADPH than with NADH. When the decarboxylase was removed by DEAE-cellulose chromatography, 4,5-dihydroxyisophthalate was identified as the product of 5-hydroxyisophthalate oxidation. A pathway for catabolism of 5-hydroxyisophthalate involving hydroxylation to 4,5-dihydroxyisophthalate followed by decarboxylation to protocatechuate, the ring-fission substrate, is proposed. Further oxidation of protocatechuate is by the ortho pathway.
Summary: Glutamine synthetase has been purified to homogeneity from two N2-fixing cyanobacteria, Anabaena cylindrica and a species of Nostoc (the phycobiont of Peltigera canina). The activities of the A. cylindrica enzyme in the biosynthetic and transferase assays were, respectively, 9.4 and 32 μmol product formed min−1 (mg protein)−1; the corresponding values for the Nostoc sp. enzyme were 6.5 and 20. Stabilization of the enzyme required Mg2+, glutamate, EDTA and a thiol reagent to be present during purification. The molecular weight of the A. cylindrica enzyme was 591000 as estimated by sedimentation analysis, 660000 by gel filtration and 565000 by polyacrylamide gel electrophoresis; the Nostoc sp. enzyme gave values of 630000 by gel filtration and 575000 by electrophoresis. The molecular weights of the sub-units of each enzyme were approximately 49000 to 50 000. Electron microscopy revealed that each molecule was composed of 12 sub-units arranged in two superimposed hexagonal rings. The maximum diameter of the rings was 13.6 nm and the distance between the centres of adjacent sub-units was 4.9 nm. When dialysed in the absence of stabilizing ligands the A. cylindrica enzyme lost activity and the protein band characteristic of the native enzyme was replaced by three bands with approximate molecular weights of 510000, 310000 and 130000. These sub-species re-associated and activity was restored by adding 2-mercaptoethanol and substrates. A similar reversible deactivation has been observed with glutamine synthetase from photosynthetic eukaryotes and yeast but no similar data have been reported for a N2-fixing prokaryote.
Summary: Exopolysaccharides and lipopolysaccharides were prepared from a number of myxobacterial strains representing the more complex types. The exopolysaccharides were isolated from fruiting bodies and from liquid and solid cultures. The polysaccharides secreted by the bacillary forms in solid or liquid media closely resembled the material obtained from fruiting bodies, the monosaccharides present being in the same approximate molar ratios. Many of the sugars present in the exopolysaccharides were also detected in the lipopoly-saccharides, suggesting an economic use of sugar nucleotide synthetic systems. Several, but not all, lipopolysaccharides contained material resembling 3-O-methylxylose in its chromatographic mobility. In addition, a faster-moving spot, as yet unidentified, was noted in some hydrolysates. The commonest monosaccharide components of the lipo-polysaccharide were rhamnose, mannose, glucose and galactose. Small quantities of amino sugars, particularly glucosamine and galactosamine, were also detected.
Summary: 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 un-affected 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 pre-treatment 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.