摘要:

Culture conditions which lead to the intracellular accumulation of arabinitol were investigated inDebaryomyces hansenii. Arabinitol, detected in very low concentrations during the exponential phase of growth, accumulated during the stationary phase of growth in yeast extract – peptone – 1% (w/v) glucose medium. This polyol was retained intracellularly even after depletion of exogenous glucose, but was rapidly depleted during regrowth in fresh glucose medium. The accumulation of arabinitol was also favoured in media containing 1% (w/v)D-fructose, sucrose,L-arabinose, glycerol, and sodium acetate. High mannitol levels accumulated in stationary phase cells derived from growth in 1% (w/v)D-mannitol, and in these cultures only traces of arabinitol were detectable. Intracellular mannitol was also retained after the extracellular mannitol had been consumed, and was rapidly depleted during regrowth in glucose medium. Arabinitol did not accumulate in basal medium with no added carbon source, nor in media with nonmetabolizable carbon sources (D-arabinose orD-ribose). On the other hand, arabinitol accumulation was independent of the initial glucose concentration between 1% (w/v) and about 9% (w/v).

ISSN:0008-4166    

DOI:10.1139/m85-087

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Klebsiella pneumoniaeserotype 1 and serotype 2 and their capsular variants were examined for production of cell-associated capsular polysaccharides and extracellular capsular polysaccharides. The virulence of these organisms in experimental animals was examined via intraperitoneal injection in mice and transtracheal inoculation into the lungs of rats. It was found that the production of either polysaccharide component correlated with the observed virulence. The extracellular polysaccharides were purified by ethanol precipitation, electrodialysis, extraction with quaternary ammonium salts, and gel filtration. These purification steps allowed for the separation and purification of both the extracellular lipopolysaccharide and the extracellular capsular polysaccharide. Purified extracellular capsular polysaccharide and extracellular lipopolysaccharide were co-injected withK.pneumoniaeintraperitoneally into mice to determine if either of these substances would produce an effect on the natural course of infection in these animals. These studies showed that only purified extracellular lipopolysaccharide enhanced the virulence ofK.pneumoniaewhen co-injected into mice, and this virulence enhancement correlated with the content of extracellular lipopolysaccharide, but not extracellular capsular polysaccharide in mixtures of these polysaccharides. Saponification ofK.pneumoniaeserotype 1 extracellular polysaccharides significantly decreased their virulence-enhancing capabilities in mice, further suggesting that extracellular lipopolysaccharide may play a role in these infections.

ISSN:0008-4166    

DOI:10.1139/m85-088

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Pyruvate kinase from the oleaginous yeastRhodosporidium toruloidesCBS 14 was partially purified and its properties investigated to determine its role during lipid production by this yeast. The enzyme (relative mass (Mr) = 190 000) showed a pH optimum of 8.0 and apparentKmvalues for K+, phosphoenolpyruvate (PEP), and ADP of 1.6 mM, 571 μM, and 120 μM, respectively. Enzyme activity was inhibited by citrate, isocitrate, ATP, GTP, and CTP and activated by fructose 1,6-bisphosphate,L-glutamate, andions. Inhibition by citrate and ATP were both competitive with PEP with theKi(citrate) = 340 μMandKi(ATP) = 303 μM. The effect of ATP and cellular energy charge were critically dependent on the concentration of ADP present in the enzyme assay. BothL-glutamate and fructose 1,6-bisphosphate increased the affinity of the enzyme for both PEP and ADP and so were significant activators at nonsaturating substrate concentrations.ions increased the affinity of the enzyme for PEP, but not ADP. The modulation of pyruvate kinase activity by such a wide range of effectors is indicative of a major regulatory role in controlling the flux of carbon, through glycolysis, into lipid-synthesizing systems.

ISSN:0008-4166    

DOI:10.1139/m85-089

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Rhizopus stoloniferandCunninghamella blakesleeanatrained after five passages to tolerate elevated concentrations of copper simultaneously acquired a tolerance to elevated levels of cadmium, cobalt, nickel, and lead. The acquired tolerance to copper was not stable in the absence of the metal, as serial transfers to a copper-free medium progressively reduced the level of tolerance, and after the sixth passage on a copper-free medium, the tolerance was equivalent to that of the nontrained parentals ("untraining"). However, the untrained fungi regained the same tolerance to copper as the original copper-trained fungi after only three passages on copper-amended medium ("retraining"). The tolerance to copper was apparently the result of physiological adaptation rather than of the selection of resistant cells or the induction of mutation. The metal may have activated genes that coded for biochemical processes that conferred tolerance to copper as well as to other heavy metals. Furthermore, the tolerance to copper of the mycelia was transferred to the sporangiospores. The copper-trained fungi did not appear to produce extracellular metabolites that complexed with and, hence, excluded and detoxified the copper. However, the mycelia of the trained fungi removed approximately twice as much copper from solution than those of the nontrained parentals, suggesting that the tolerance to copper resulted from the binding of the metal to the cell wall or from an intracellular detoxification mechanism.

ISSN:0008-4166    

DOI:10.1139/m85-090

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

In estuarine sediments with a high degree of vertical heterogeneity in reduced substrate and terminal electron acceptor concentrations, the method of exposure of the microbiota to labeled substrates can introduce a "disturbance artifact" into measures of metabolic activity. The detection of this artifact is based on a quantitative measurement of the relative rates of incorporation of [14C]acetate into phospholipid fatty acids (PLFA) and endogenous storage lipid, poly-beta-hydroxyalkanoate (PHA). Previous studies have shown that PLFA synthesis measures cellular growth and that PHA synthesis measures carbon accumulation (unbalanced growth). The "disturbance artifact" of exposure to [14C]acetate was demonstrated by comparing injection of a core with the usual or pore-water replacement or slurry techniques. Only injection of labeled substrate allowed detection of a preassay disturbance of the sediment with a garden rake. The raking increased PLFA synthesis with little effect on PHA synthesis. The differences between injection and slurry inoculation techniques on disturbed sediments were not due to differences in concentration or distribution of [14C]acetate in the 10-min incubation. Bioturbation induced by sand dollar feeding in estuarine sediment could be detected in an increased PLFA/PHA ratio which was due to decreased PHA synthesis if the addition of labeled substrate was by the injection technique. Addition of labeled precursors to sediment by slurry or pore-water replacement induces greater disturbance artifacts than injection techniques.

ISSN:0008-4166    

DOI:10.1139/m85-091

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Forty-eight bacterial strains isolated from decaying bark were cultivated in a mineral medium with added quebracho and mimosa tannin extracts as carbon sources. The degradation of the two condensed tannins by each bacterial strain was compared by means of two dosage methods permitting estimations of the astringent capacity losses and the attack of the flavane-3-ols groups. For an even incubation period, tannin from mimosa was more strongly degraded than that from quebracho, and depolymerization was much more important than the attack of monomeric structures. These results confirmed the aptitude of those bacteria to degrade condensed tannins, and thus practical utilisation can be foreseen for such strains.[Translated by the journal]

ISSN:0008-4166    

DOI:10.1139/m85-092

出版商:NRC Research Press    

年代:1985

数据来源: NRC

ISSN:0008-4166    

DOI:10.1139/m85-093

出版商:NRC Research Press    

年代:1985

数据来源: NRC