- Volume 96, Issue 2, 1976

SUMMARY: The activity of nitrate reductase in Rhizobium japonicum is controlled by oxygen tension, and not by nitrate. The enzyme from R. japonicum grown anaerobically in the presence of nitrate resembles that from bacteroids in having a molecular weight of about 69000 daltons; the enzyme from aerobically grown cells has a molecular weight of about 170000 daltons. Both types of enzyme have similar K m values, but differ in their sensitivity to KCN.

SUMMARY: Pseudomonas aeruginosa pac7 (a mutant deficient in diaminopimelate epimerase), excreted diaminopimelate (solely ll-isomer) after growth in a minimal medium plus lysine with succinate as carbon source. More diaminopimelate was excreted when bacteria were transferred at the end of the exponential phase of growth into fresh minimal medium without lysine but supplemented with pyruvate and additional (NH4)2SO4. The excreted LL-isomer was isolated from the culture filtrate by ion-exchange chromatography and purified by crystallization (17 g/9 1 culture).

A diaminopimelate-requiring mutant of Bacillus megaterium ncib7581 grew on ll- and/or meso-diaminopimelate but not on the dd-isomer. This mutant was used to isolate the dd-isomer from a mixture of synthetic ll- and dd-diaminopimelate. It was grown in a minimal medium containing glycerol as carbon source and ll-plus dd-diaminopimelate at a growth-limiting concentration (300 mg l−1); when growth stopped, the dd-diaminopimelate that remained in the culture was isolated and crystallized (10 g/11 l culture).

SUMMARY: Formation of benzoate and catechol during oxidation of benzyl alcohol by washed suspensions of Acinetobacter calcoaceticus ncib8250 confirmed earlier results indicating that this organism metabolizes benzyl alcohol via benzaldehyde, benzoate, and the 3-oxoadipate pathway. There was no evidence for feedback inhibition of benzyl alcohol dehydrogenase or benzaldehyde dehydrogenase II. Examination of growth curves and patterns of substrate utilization, as well as measurement of enzyme activities, showed that benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase II are repressed when A. calcoaceticus utilizes l-mandelate or phenylglyoxylate. Growth of bacteria on l-mandelate prior to their inoculation into benzyl alcohol/salts medium leads to an exceptionally long lag period before benzyl alcohol is used at the maximum rate. Benzyl alcohol metabolism is also suppressed during growth on benzoate.

SUMMARY: Lipopolysaccharide (LPS) of Pseudomonas morsprunorum was extracted with hot phenol and purified by repeated centrifuging followed by either block electrophoresis or gel filtration. LPS from a virulent isolate exhibited specific phage inactivation (PI50 = 0·05 μg LPS ml−1), whereas LPS from an avirulent phage-resistant mutant did not. LPS was considered pure when a single band was detected following sodium dodecyl sulphate-cellulose acetate electrophoresis (pH 7·4). It was not phytotoxic when inoculated into cherry leaves at concentrations up to 1 mg ml−1, but produced weak chlorosis in bean and tobacco at 2mg ml−1: no visible symptoms appeared after treatment with lower concentrations. The chemical composition of the LPS was partly determined.

SUMMARY: Bacitracin markedly increased the toxic effect of several divalent metal ions towards growth of the producer strain Bacillus licheniformis atcc14580. Magnesium ions antagonized the toxic effect of these divalent cations both in the presence and absence of bacitracin. It is suggested that bacitracin increases the uptake of several divalent metal ions. The function of the bacitracin peptides may be to extract essential divalent cations from ‘waiting sites’ on the surface of the cells and transfer the cations to the transport mechanisms in the cytoplasmic membrane.

SUMMARY: The effects of different nutrient limitations on the production of the two enzymes of gramicidin S biosynthesis were studied during continuous culture of Bacillus brevis. Gramicidin S synthetases I and II were produced in the chemostat under carbon, nitrogen, phosphorus or sulphur limitation. The growth rate, rather than the nature of the limitation, was the major controlling factor in regulating the level of the gramicidin S synthetases. Synthetase production was low at high dilution rates (0·45 to 0·50 h−1) but increased as the dilution rate was lowered. The highest specific activities occurred at dilution rates that were different for each type of limitation: 0·40 h−1 for nitrogen, 0·32 h−1 for carbon, 0·24 h−1 for sulphur and 020 h−1 for phosphorus. Phosphorus limitation gave the highest specific activities. At low dilution rates (0·10 to 0·15 h−1), enzyme activities were again low. Sporulation occurred under carbon limitation, but at a lower dilution rate than that which supported optimal gramicidin S synthetase formation. The specific productivity of the synthetases in the chemostat was higher than the highest productivity obtained in batch growth.

SUMMARY: Electron microscopic observations of an indigotin-producing dome mutant of Schizophyllum commune Fr. have shown that large wall ingrowths occur within the hyphae. These ingrowths are coupled with morphological abnormalities produced by the dome mutation. The pigment indigotin appears to be produced by progressive condensation within vacuoles and to a lesser extent within the wall ingrowths. Cytochemical techniques have shown that the wall ingrowths are similar in structure to the hyphal walls. There was no evidence for the passage of condensed indigotin into the medium; the pigment granules found in the medium must therefore form outside the hyphae.

SUMMARY: Streptomyces coelicolor A3(2) synthesizes a second antibiotic, in addition to the plasmid-determined methylenomycin A. It was identified, primarily on the evidence of mass spectroscopy of its diethyl ester, as actinorhodin, which has been described previously in other strains. It inhibited most Gram-positive bacteria tested, but only at a comparatively high concentration. Five independent mutations leading to lack of actinorhodin synthesis were located between CYSD and STRA on the chromosome.

SUMMARY: Twelve bld mutations of Streptomyces coelicolor resulting in a lack of visible aerial mycelium were mapped genetically. The mutants were classified into three groups on the basis of colony morphology, production of antibiotics and morphology on different carbon sources. Four map locations were found for the bld genes and three of these were very near the loci of whi genes, which are also involved in differentiation. Closely linked bld mutations had similar phenotypes.

SUMMARY: Strains of Escherichia coli that are unable to grow on fructose because they lack the phosphoenolpyruvate: fructose phosphotransferases specified by ptsF and ptsX mutate to grow on media containing fructose as sole carbon source, but do not regain the function of either of the missing phosphotransferases. Instead, fructose is taken up and phosphorylated to fructose 6-phosphate by a phosphoenolpyruvate: sorbitol phosphotransferase which, in wild-type cells, is induced by sorbitol but not by fructose, but which is constitutively expressed in these mutants. The regulatory gene srlC controlling enzymes of sorbitol uptake and catabolism has been located on the E. coli genome as part of the linkage group cysI srlC att186 pheA.

SUMMARY: Attempts to study quantitatively the phagocytosis of gonococci from urethral pus failed because of the small numbers of organisms and technical difficulties. However, gonococci from chambers implanted subcutaneously in guinea pigs, which were similar to gonococci from urethral pus in their resistance to killing by human serum, were obtained in sufficient quantities for comparison in phagocytosis tests with the in vitro grown strain from which they were derived.

Microscopic and viable counts of gonococci in phagocytes showed that in vivo grown organisms (strain BSV) were readily phagocytosed by human polymorphonuclear phagocytes. There was little difference between BSV organisms and the in vitro grown organisms (strain BS) in resistance to ingestion. There was, however, a marked difference in the intracellular survival of strains BSV and BS during the first hour of phagocytosis. Whereas BSV organisms survived well, many BS organisms were killed. Subsequently, strain BSV and the survivors of the strain BS inoculum responded similarly to the intracellular bactericidins. These results were supported by electron microscopy of infected phagocytes.

Resistance of gonococci in vivo to ingestion and digestion by human phagocytes seem to be important facets of the pathogenesis of gonorrhoea.

SUMMARY: Isoelectric focusing showed that Neisseria gonorrhoeae has an overall negative surface charge. Chemical modification of protein amino or carboxyl groups changed the surface charge and thereby altered the ability of the organisms to attach to human amnion cells grown in tissue culture. Attachment of modified and unmodified N. gonorrhoeae was increased by the presence of pili only when the bacteria bore a negative surface charge. Thus an important factor in the pathogenesis of gonorrhoea may be the ability of pili to facilitate attachment of N. gonorrhoeae by overcoming the initial electrostatic repulsive barrier which exists between it and the host cell.

SUMMARY: The composition of the amino-acid pool of Saccharomyces cerevisiae is markedly influenced by the amino-acid nitrogen source. The yeast tends to accumulate the amino acid supplied and those closely related to it metabolically. A relatively high concentration of glutamic acid is maintained in the pools of all cultures irrespective of the nitrogen source, reflecting the central role of glutamic acid in nitrogen metabolism. The total amino-acid pool concentration increases as a function of growth rate, although differences exist in the behaviour of individual amino acids.

SUMMARY: A static ampoule microcalorimeter was used to study the growth of mycoplasmas, acholeplasmas and ureaplasmas. Growth as indicated by thermograms was compared with the results of conventional methods, namely, terminal dilution counts, plate counts, turbidimetric measurements, glucose consumption and pH changes. Removal of oxygen had little effect on mycoplasma growth. The microcalorimetric method is potentially useful for identifying and enumerating the members of the Mycoplasmatales.

SUMMARY: Previous work led to the separation from seminal plasma of a peptide fraction which promoted a high rate of germination of blastospores of Candida albicans. It has now been shown that an acid hydrolysate of this material is also highly active. A minimal amino-acid mixture consisting of aspartic acid, lysine, histidine, threonine, proline and -alanine gave 90% germination in 4 h with 17 out of 28 strains examined. Glucose and inorganic phosphate were also required. Phosphate was not required for the activity of the original peptide fraction.