The effect of nickel (Ni2+) and N-starvation on urea metabolism was studied in the unicellular cyanobacterium Anacystis nidulans. The cells subjected to N-starvation showed only variation in urease activity levels, which disappeared with the supplementation of Ni2+ to the growth medium after sterilization. The addition of Ni2+ also increased the urease activity levels. The cells deprived of nitrogen (without Ni2+) showed a low level of urease activity; however, the ability to take up urea increased significantly. The N-deprived cells grown with Ni2+ showed maximum urease activity which remained constant over a period of 24h. NH4+-grown cells showed negligible urea uptake and urease activity which in creased by transferring these cells in N2-medium. The ability to take up and hydrolyze urea required approximately 6 to 12h for maximum expression. Erythromycin (50μg ml-1) completely prevented the derepression in urea uptake and urease systems. The cells treated with erythromycin in combination with Ni2+ showed a higher level of urease activity as compared to erythromycin-treated cells only.
This study was undertaken to clarify the taxonomy of the pink-pigmented nitrogen-fixing bacteria isolated from the rhizosphere of rice and previously referred to as Protomonas-like bacteria (Oyaizu-Masuchi, Y. and Komagata, K., J. Gen. Appl. Microbiol., 34, 127-164 (1988)); also to investigate their capacity for nitrogen fixation. The ability of the isolates to grow anaerobically under photoheterotrophic conditions as well as aerobic chemotrophic conditions demonstrate that they are a member of anoxygenic phototrophic purple bacteria. Based on the phenotypic and chemotaxonomic tests and DNA-DNA hybridization assays, it was concluded that the isolates should be assigned to Rhodopseudomonas palustris. All these isolates grew with N2 as the sole nitrogen source under both anaerobic-light and microaerobic-dark conditions, and showed significant in vivo nitrogenase activity.
When Clostridium perfringens type A NCTC 8798 was grown in Duncan and Strong sporulation medium, spore formation and enterotoxin production coincided with each other, and a similar intimate relationship was observed between the sporulation and cytoplasmic inclusion body formation. The initiation of an exponential increase of the enterotoxin production was correlated with the sporulation stage III; at that time forespore formation was first seen by electron microscopy. When spore cortex become visible (stage V of sporulation), the inclusion body appeared. Enterotoxigenic cells and nontoxigenic mutants which differed in their sporulating abilities were examined for inclusion body formation. The results showed a close relation between sporulation, enterotoxin production, and inclusion body formation.
3-Decynoyl N-acetylcysteamine (DNAC), a specific inhibitor of the anaerobic pathway for bacterial unsaturated fatty acid synthesis, completely inhibited the growth of a psychrotrophic bacterium, Pseudomonas sp. strain E-3 (Pseudomonas E-3), in a succinate-salt medium. But the DNAC-inhibited growth was effectively relieved by supplementing saturated fatty acid in the medium. Although the in vitro synthesis of unsaturated fatty acid was inhibited by DNAC, it became insensitive to DNAC when fatty acid synthase was assayed in the presence of the membrane fraction containing Δ9 fatty acyl-CoA desaturase. When Pseudomonas E-3 was grown on pentadecanoate, a fatty acid unnatural to this bacterium, the cells contained penta- and heptadecenoate in the phospholipid, and the content of these odd-numbered unsaturated fatty acids amounted to 57% of the total unsaturated fatty acids. By cleavage of the penta- and heptadecenoate with periodate/ permanganate, they were identified as Δ9 15:1 and Δ9 17:1, respectively. All this indicates that the aerobic fatty acid desaturase system evidently contributes to in vivo formation of at least a part of unsaturated fatty acids in this bacterium.
When copper-resistant Escherichia coli HB101 cells were transferred from regular to copper-amended, 1/3 strength Tryptic Soy Broth (TSB), there was an increase in the amount of exopolymer produced. The copper binding abilities of exopolymer for Pseudomonas aeruginosa 7, P. pseudomallei 13-1 (both copper-resistant) and from P. putida 3 (copper-sensitive), were also determined. If treated with phenol, about 50 to 75% of the copper binding ability of these exopolymers was removed. Although the amount of copper ion bound by the exopolymer isolated from P. putida 3 was about the same as from the resistant organisms, it did not grow in medium containing 0.5ppm copper ion. When free copper ion concentration in 1/3 strength TSB increased to 0.5ppm, the pH value of the broth dropped from 6.8 to 4.9. We believe this was what prevented the growth of the P. putida 3 in the solution containing the high concentration of copper ion.
Metabolically active heterocysts isolated from wild type Anabaena sp. strain CA under hydrogen incubation showed high endogenous acetylene-reducing activity with or without nickel supplementation. The acetylene reducing activity of Ar-incubated heterocysts was significantly enhanced by fructose, erythrose, and reduced glutathione. The possible pathways related to reductant supply to heterocysts are discussed.
The metabolic pathway of phenol was examined in the yeast strains of Rhodotorula (R.) rubra IFO 0892 and 1101. Changes in concentrations of phenol, phenol metabolites and dissolved organic carbon (DOC) in a medium were determined during incubation of phenol-grown cells with a phenol solution. A decrease in DOC concentration indicated that phenol was used as a carbon source. The phenol metabolites were separated and identified using high performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS). For HPLC analysis of β-ketoadipic acid, 2, 4-dinitrophenylhydrazone derivative was prepared. This analysis is very selective and sensitive. For GC/MS analysis, metabolites in the cultured broth were extracted with ethyl acetate and trimethylsilylated using N, o-bis(trimethylsilyl)acetoamide. Formation of muconolactone and β-ketoadipate enol-lactone from phenol was studied using whole cells. β-Ketoadipic acid was produced from muconolactone by the crude cell-free extract of R. rubra IFO 0892 and 1101. From the results in this study, a metabolic sequence for phenol degradation is proposed. Phenol may be hydroxylated to form catechol prior to ring cleavage, and catechol may be further oxidized to cis, cis-muconic acid, muconolactone, β-ketoadipate enol-lactone and β-ketoadipic acid. The catechol branch in the, β-ketoadipate pathway may exist in R. rubra and this catechol may be oxidized by the ortho type of ring fission.
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