Soil bacterial flora was studied in soil suspensions supplied with cellulose powder. Cellulose decomposers proliferated comparatively soon after addition of the cellulose powder. Following the proliferation of the cellulose decomposers, counts of total numbers of non-cellulolytic bacteria increased in proportion to the amount of added cellulose powder. Bacteriological characterization of the isolated bacterial strains revealed that gram-negative bacteria, especially pseudomonad groups, increased their populations in soil suspensions with the added cellulose powder. On the other hand, the bacillus group did not increase even under such conditions. Most of the predominant gram-negative bacteria could grow by utilizing glucose or cellobiose as the sole source of carbon. At the final stage of the experimental period, the predominance of the gram-negative bacteria diminished, and these organisms were partly replaced by bacteria which were unable to utilize glucose or cellobiose. The change in pH of the soil suspensions and the pattern of accumulation of reducing sugars were also followed. A fungus predominated temporarily during the decomposition of cellulose when the pH of the soil suspension was lowered.
The gene order around amyE+ and aroI+ of the B. subtilis chromosomal DNA is lint-tmrA-amyR-amyE-tmrB-aroI (J. Bacteriol., 136: 818-821, 1978). After EcoRI-digestion of the DNA, tmrB and aroI+ were included in one DNA fragment but amyE+ was not. The tmrB aroI+ DNA fragment generated by EcoRI-digestion of the chromosomal DNA from B. subtilis B8 was cloned in a temperate B. subtilis phage ρ11 genome. The molecular size of the EcoRI-insert containing tmrB and aroI+ in the constructed transducing phage genome was 5.14kb. The fragment was recloned in E. coli vector systems, λgtWES and pBR322. The recombinant plasmid was designated as pTUE1. The tmrB aroI+ DNA fragment generated by EcoRI-digestion of the chromosomal DNA from B. subtilis T2N26, an ultrahyper α-amylase producing strain, was directly cloned in another vector system, charon 4A, using [32P]-labeled pTUE1 as a probe. The molecular size of the tmrB aroI+ fragment inserted in the recombinant phage (λ144A) genome was 11.7kb. Southern hybridization analysis using the two tmrB aroI+ DNA fragments showed that the molecular size of the EcoRI fragments from the B8 and T2N26 chromosomal DNA were 13.5kb and 11.7kb, respectively. The physical map of the aroI+ gene regions was differerent between the B8 T2N26 chromosomal DNA. The physical maps of the EcoRI-fragments containing the tmrB aroI+ genes of pTUE1 and the B8 chromosomal DNA were quite different but they hybridized. The small molecular size of the DNA fragment from pTUE1 seemed to be caused by deletion(s) which might have occurred at the construction and stabilization of the tmrB aroI+ genes in the ρ11 genome.
A rapid and simple method for large-scale preparation of phosphoenolpyruvate carboxylase [EC 126.96.36.199] from Escherichia coli K-12 was established. A strain carrying the ColE1-ppc+ (the gene of the enzyme) hybrid plasmid was used as an enzyme source. The cell-free extract was fractionated by ammonium sulfate, and the enzyme was purified to homogeneity by hydrophobic chromatography on hexyl-Sepharose using specific elution with L-aspartate, one of the allosteric effectors. The pure enzyme (153mg) was obtained from 137g wet cells in 4 days with 41% yield.
This is a report on whether and in what manner the metabolic activity of Escherichia coli is affected when liquid normal alkanes such as hexane, octane, decane to hexadecane and octadecane are dispersed in the cell suspension. Among these alkanes, dodecane, tridecane and tetradecane markedly enhanced the respiratory activity and depressed the rate of glucose uptake. The other alkanes did not show such marked effects. The ratio of glucose metabolized by respiration (respiratory ratio), calculated from the amount of oxygen and glucose taken up by E. coli, was inversely proportional to the rate of glucose uptake. The number and the activity of the cells adsorbed to these alkanes were too small to be detected. These effects of the alkanes on the activities of the organism were reversible as indicated by their disappearance after the removal of the alkanes from the cell suspension. Consequently the organism received these effects reversibly from the interface between the alkanes and the cell suspension. These results coincide with those obtained with solid hydrophobic materials (1). A notable relation was found between the interface effect and the surface tension of the alkanes, in which the interface effect has a maximum at the tension of 24-26dyn/cm.
6-Methoxymellein (6MM), a phytoalexin of carrot, exerted a static effect on the growth of fungi, yeast and bacteria at low concentrations. It retarded the spore germination of Chaetomium globosum and extended the lag phase in the growth of Bullera alba, Candida albicans and Staphylococcusaureus. When B. alba and C. albicans were first treated with 6MM and then a second time their growth was not inhibited by the second dose, suggesting that they become tolerant to 6MM through some induced factor. By contrast, S. aureus appeared to tolerate 6MM in a constitutive manner, since the bacterial growth was inhibited by the second dose of 6MM as well as the first. In S. aureus culture, however, the duration of growth inhibition by 6MM was dependent on the inoculum size, and the inhibitory effect was negligible when the bacterial concentration in the culture was sufficiently high. Chaetomium globosum and B. alba incorporated appreciable amounts of 6MM, but no metabolite of the phytoalexin appeared in the culture. The results suggest that 6MM tolerance occurred in these microorganisms independently of its degradation or transformation.
Successful adaptation of sludge to 24 out of 35 phenolic and benzoic acid derivatives was achieved by incubating domestic activated sludge samples with increasing amounts of the various compounds tested. In addition, with manometric techniques it was found that sludges which had adapted to one compound were able to oxidize other compounds to which they had not been previously exposed. However, no strict relationship between the nature and position of substituents in the aromatic ring and the effectivness of the processes of acclimation was found.
The cells of Thiobacillus ferrooxidans were rapidly adsorbed on the solid surfaces of an agitated flask containing 1% pulp density of pyrite particles. More than ca. 99% of the inoculated cells were adsorbed. However, considerably fewer cells were adsorbed on pyrite particles than on the glass wall of the flask. Scanning electron microscope observation revealed that T. ferrooxidans cells were adsorbed aggregatively on restricted areas of the pyrite particles. The surfaces of the pyrite particles were characteristically eroded to show etched polyhedral pits, but without prominent cell adsorption of the extensively eroded surfaces during markedly enhanced leaching. When T. ferrooxidans cells were adsorbed on the solid surfaces, the iron-oxidizing activity of the bacteria was strongly inhibited, resulting in a failure to enhance pyrite oxidation. Adsorbed cells did not proliferate on the solid surfaces. When the adsorbed cells were released into an aqueous phase by the addition of the surface active agent Tween 20, the bacterial iron-oxidizing activity inhibited by adsorption was recovered and, as a result, pyrite oxidation was markedly promoted. Significant enhancement of pyrite oxidation by T. ferrooxidans was ascribed to the development and iron-oxidizing activity of the freely dispersed cells in an aqueous phase. The function of the surface active agent is to prevent tenacious adsorption of the bacterial cells to solid surfaces and organic substances examined, such as protein, nucleic acid, yeast extract, peptone, and cell free extracts, operate in the same way as the surface active agent. The enhancement of the bacterial pyrite oxidation by the intact cells of Thiobacillus thiooxidans is thought to be attributable to the organic substances excreted from T. thiooxidans cells and/or to the exchange adsorption of cells of both thiobacilli. The present results indicate that bacterial concentration in an aqueous phase rather than on pyrite particles plays major role in the enhanced oxidation of pyrite by T. ferrooxidans and that the bacteria contribute indirectly to pyrite oxidation through the regeneration reaction of ferric iron.
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