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O M Neijssel

Publications and source records attributed to O M Neijssel.

At least 37 records · Page 2Linked to original sources
PubMed1990

The role of magnesium and calcium ions in the glucose dehydrogenase activity of Klebsiella pneumoniae NCTC 418.

Magnesium-limited chemostat cultures of Klebsiella pneumoniae NCTC 418 with 20 microM CaCl2 in the medium showed a low rate of gluconate plus 2-ketogluconate production relative to potassium- or phosphate-limited cultures. However, when the medium concentration of CaCl2 was increased to 1 mM, the glucose dehydrogenase (GDH) activities also increased and became similar to those observed in potassium- or phosphate limited cultures. It is concluded that this is due to Mg2+ and Ca2+ ions being involved in the binding of pyrroloquinoline quinone (PQQ) to the GDH apoenzyme. There seems to be an absolute requirement of divalent cations for proper enzyme functioning and in this respect Ca2+ ions could replace Mg2+ ions. The high GDH activity which has been found in cells grown under Mg2(+)-limited conditions in the presence of higher concentrations of Ca2+ ions, is compatible with the earlier proposal that GDH functions as an auxiliary energy generating system involved in the maintenance of high transmembrane ion gradients.

Calcium↗
PubMed1990

Involvement of pyruvate dehydrogenase in product formation in pyruvate-limited anaerobic chemostat cultures of Enterococcus faecalis NCTC 775.

Enterococcus faecalis NCTC 775 was grown anaerobically in chemostat culture with pyruvate as the energy source. At low culture pH values, high in vivo and in vitro activities were found for both pyruvate dehydrogenase and lactate dehydrogenase. At high culture pH values the carbon flux was shifted towards pyruvate formate lyase. Some mechanisms possibly involved in this metabolic switch are discussed. In particular attention is paid to the NADH/NAD ratio (redox potential) and the fructose-1,6-bisphosphate-dependent lactate dehydrogenase activity as possible regulatory factors.

Acetyltransferases↗
PubMed1989

The separate roles of PQQ and apo-enzyme syntheses in the regulation of glucose dehydrogenase activity in Klebsiella pneumoniae NCTC 418.

No holoenzyme pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase and only very low apoenzyme levels could be detected in cells of Klebsiella pneumoniae, growing anaerobically, or carrying out a fumarate or nitrate respiration. Low glucose dehydrogenase activity in some aerobic glucose-excess cultures of K. pneumoniae (ammonia or sulphate limitation) was increased significantly by addition of PQQ, whereas in cells already possessing a high glucose dehydrogenase activity (phosphate or potassium limitation) extra PQQ had almost no effect. These observations indicate that the glucose dehydrogenase activity in K. pneumoniae is modulated by both PQQ synthesis and synthesis of the glucose dehydrogenase apo-enzyme.

Aerobiosis↗
PubMed1989

The influence of the culture pH value on the direct glucose oxidative pathway in Klebsiella pneumoniae NCTC 418.

Klebsiella pneumoniae NCTC 418 was cultured aerobically in chemostat cultures (D = 0.3 h-1; 35 degrees C) under respectively carbon-, phosphate-, potassium-, sulphate-, and ammonia-limited conditions with glucose as the sole carbon and energy source. The effect of the external pH value on glucose metabolism and on the enzymes of the direct glucose oxidative pathway was examined. The pH value of the medium had a profound influence on both the activity and the synthesis of the glucose dehydrogenase and the gluconate dehydrogenase. At pH values ranging from pH 5.5 to pH 6.0 maximal activity and synthesis of these enzymes resulted in a more than 80% conversion of the glucose consumed into gluconate and 2-ketogluconate under potassium- or phosphate-limited conditions. On the other hand, no gluconate and/or 2-ketogluconate production could be detected when K. pneumoniae was cultured at pH 8.0. Whereas the synthesis of gluconate dehydrogenase seemingly was completely repressed, still some glucose dehydrogenase was present. The lack of glucose dehydrogenase activity at pH 8.0 was shown not to be due to the dissociation of the cofactor PQQ from the enzyme.

Aerobiosis↗
PubMed1989

Replacement of potassium ions by ammonium ions in different micro-organisms grown in potassium-limited chemostat culture.

The biomass concentration extant in potassium-limited cultures of either Klebsiella pneumoniae or Bacillus stearothermophilus (when growing at a fixed temperature and dilution rate in a glucose/ammonium salts medium) increased progressively as the medium pH value was raised step-wise from 7.0 to 8.5. Because the macromolecular composition of the organisms did not vary significantly, this increase in biomass could not be attributed to an accumulation of storage-type polymers but appeared to reflect a pH-dependent decrease in the cells' minimum K+ requirement. Significantly, this effect of pH was not evident with cultures in which no ammonium salts were present and in which either glutamate or nitrate was added as the sole nitrogen source; however, it was again manifest when various concentrations of NH4Cl were added to the glutamate-containing medium. This suggested a functional replacement of K+ by NH4+, a proposition consistent with the close similarity of the ionic radii of the potassium ion (1.33 A) and the ammonium ion (1.43 A). At pH 8.0, and with a medium containing both glutamate (30 mM) and NH4Cl (100 mM), cultures of B. stearothermophilus would grow without added potassium at a maximum rate of 0.7 h-1. Under these conditions the cells contained maximally 0.1% (w/w) potassium (derived from contaminating amounts of this element in the medium constituents), a value which should be compared with one of 1.4% (w/w) for cells growing in a potassium-limited medium containing initially 0.5 mM K+.(ABSTRACT TRUNCATED AT 250 WORDS)

Culture Media↗
PubMed1989

Physiological significance and bioenergetic aspects of glucose dehydrogenase.

The regulation of the PQQ-linked glucose dehydrogenase in different organisms is reviewed. It is concluded that this enzyme functions as an auxiliary energy-generating mechanism, because it is maximally synthesized under conditions of energy stress. It is now definitively established that the oxidation of glucose to gluconate generates metabolically useful energy. The magnitude of the contribution of the oxidation of glucose to gluconate via this enzyme to the growth yield of organisms such as Acinetobacter calcoaceticus is not yet clear.

Bacteria↗
PubMed1989

Nitrogen-limited behaviour of micro-organisms growing in the presence of large concentrations of ammonium ions.

Cells of Klebsiella pneumoniae NCTC 418 grown at low culture pH values (4.5-5) in a glucose-limited chemostat culture contained elevated levels of glutamate synthase (EC 2.6.1.53). This can be taken as an indication that these cells show the physiology of nitrogen-limited cells, in spite of the fact that high concentrations (about 80 mM) of ammonium ions were present in the culture extracellular fluids. This phenomenon can be explained by the rapid diffusion of ammonia (NH3) through the cell membrane, leading to very low cytoplasmic ammonium (NH4+) and NH3 levels in cells that possess an almost neutral cytoplasmic pH value, but are growing at low culture pH values.

Ammonia↗
PubMed1987

PQQ-linked enzymes in enteric bacteria.

Klebsiella aerogenes possesses a PQQ-linked glucose dehydrogenase. Other members of the Enterobacteriaceae, such as Escherichia coli, Salmonella typhimurium or Serratia marcescens are seemingly unable to synthesize PQQ, but are able to synthesize the glucose dehydrogenase apoenzyme. The physiological significance of this enzyme is discussed.

Coenzymes↗
PubMed1985

The functional significance of glucose dehydrogenase in Klebsiella aerogenes.

In order to assess the functional significance of the quinoprotein glucose dehydrogenase recently found to be present in K+ -limited Klebsiella aerogenes, a broad study was made of the influence of specific environmental conditions on the cellular content of this enzyme. Whereas high activities were manifest in cells from glucose containing chemostat cultures that were either potassium- or phosphate-limited, only low activities were apparent in cells from similar cultures that were either glucose-, sulphate- or ammonia-limited. With these latter two cultures, a marked increase in glucose dehydrogenase activity was observed when 2,4-dinitrophenol (1 mM end concentration) was added to the growth medium. These results suggested that the synthesis of glucose dehydrogenase is not regulated by the level of glucose in the growth medium, but possibly by conditions that imposed an energetic stress upon the cells. This conclusion was further supported by a subsequent finding that K+ -limited cells that were growing on glycerol also synthesized substantial amounts of glucose dehydrogenase. The enzyme was found to be membrane associated, and preliminary evidence has been obtained that it is located on the periplasmic side of the cytoplasmic membrane and functionally linked to the respiratory chain. This structural and functional orientation is consistent with glucose dehydrogenase serving as a low impedance energy generating system.

Carbohydrate Dehydrogenases↗
PubMed1985

Metabolic and energetic aspects of the growth of Clostridium butyricum on glucose in chemostat culture.

The influence of a number of environmental parameters on the fermentation of glucose, and on the energetics of growth of Clostridium butyricum in chemostat culture, have been studied. With cultures that were continuously sparged with nitrogen gas, glucose was fermented primarily to acetate and butyrate with a fixed stoichiometry. Thus, irrespective of the growth rate, input glucose concentration, specific nutrient limitation and, within limits, the culture pH value, the acetate/butyrate molar ratio in the culture extracellular fluids was uniformly 0.74 +/- 0.07. Thus, the efficiency with which ATP was generated from glucose catabolism also was constant at 3.27 +/- 0.02 mol ATP/mol glucose fermented. However, the rate of glucose fermentation at a fixed growth rate, and hence the rate of ATP generation, varied markedly under some conditions, leading to changes in the Y glucose and YATP values. In general, glucose-sufficient cultures expressed lower yield values than a corresponding glucose-limited culture, and this was particularly marked with a potassium-limited culture. However, with a glucose-limited culture increasing the input glucose concentration above 40 g glucose X 1(-1) also led to a significant decrease in the yield values that could be partially reversed by increasing the sparging rate of the nitrogen gas. Finally glucose-limited cultures immediately expressed an increased rate of glucose fermentation when relieved of their growth limitation. Since the rate of cell synthesis did not increase instantaneously, again the yield values with respect to glucose consumed and ATP generated transiently decreased. Two conditions were found to effect a change in the fermentation pattern with a lowering of the acetate/butyrate molar ratio. First, a significant decrease in this ratio was observed when a glucose-limited culture was not sparged with nitrogen gas; and second, a substantial (and progressive) decrease was observed to follow addition of increasing amounts of mannitol to a glucose-limited culture. In both cases, however, there was no apparent change in the YATP value.(ABSTRACT TRUNCATED AT 250 WORDS)

Clostridium↗
PubMed1984

Influence of metabolic end-products on the growth efficiency of Klebsiella aerogenes in anaerobic chemostat culture.

Progressively increasing the input concentration of growth-limiting nutrient (glucose, ammonia, K+) to anaerobic chemostat cultures of Klebsiella aerogenes (D = 0.38 h-1; 35 degrees C; pH 6.8) led to a non-linear increase in bacterial cell concentration. At modest population densities, residual growth-limiting substrate levels increased substantially, with increasing input concentration, and the culture bacterial dry weight tended to a constant value. With the glucose-limited culture, increasing the glucose input concentration above 20 g X 1(-1) led to accumulation of unused glucose and a change in the fermentation pattern. There was a concomitant lowering of the yield value with respect to glucose consumption, and the calculated YATP value similarly declined. Addition of extra essential (non-limiting) nutrients to the culture was without effect. Similarly, addition of individual fermentation products (acetate, ethanol, D-lactate, 2,3-butanediol, succinate) to the feed medium, in varying concentrations and in different combinations, failed to influence the fermentation pattern or the energetics of cell synthesis. However, a clear correlation was observed between the yield values (of both glucose- and K+-limited cultures) and the steady state concentration of CO2 in the effluent gas. Increasing the concentration CO2 either by increasing the population density or lowering the sparging rate of nitrogen gas through the culture, effected a lowering of the yield values. It is suggested that dissolved CO2 exerts an effect on both metabolism and the energetics of cell synthesis. A possible mechanism of energy dissipation (i.e., a futile cycle) involving carboxylation and decarboxylation reactions is proposed.

Acetates↗
PubMed1982

Generality of the growth kinetics of the average individual cell in different bacterial populations.

The kinetics of growth of all the cells in a population is reflected in the shape of the size distribution of the population. To ascertain whether the kinetics of growth of the average individual cell is similar for different strains or growth conditions, we compared the shape of normalized size distributions obtained from steady-state populations. Significant differences in the size distributions were found, but these could be ascribed either to the precision achieved at division or to a constriction period which is long relative to the total cell cycle time. The remaining difference is quite small. Thus, without establishing the pattern itself, it is concluded that the basic course of growth is very similar for the various Escherichia coli strains examined and probably also for other rod-shaped bacteria. The effects of differences in culture technique (batch or chemostat culture), growth rate, and differences among strains were not found to influence the shape of the size distributions and hence the growth kinetics in a direct manner; small differences were found, but only when the precision at division or the fraction of constricted cells (long constriction period) were different as well.

Bacillus megaterium↗
PubMed1980

Influence of growth environment on the phosphoenolpyruvate: glucose phosphotransferase activities of Escherichia coli and Klebsiella aerogenes: a comparative study.

A consistent difference was found between glucose-limited cultures of Escherichia coli and Klebsiella aerogenes strains in the manner which their apparent cellular content of glucose:phosphoenolpyruvate phosphotransferase (glucose-PTS) varied with growth rate. With the former strains, activity increased as a function of growth rate; in the latter it decreased. However, under glucose-sufficient conditions (potassium- or ammonia-limitation) both species behaved similarly; the glucose-PTS activity was lower and bore no obvious relationship to the rate of glucose consumption expressed by the growing culture. These results are discussed in relation to the role of glucose as a regulator of glucose-PTS synthesis, and to the likely contribution which the glucose-PTS makes to the overall rate of glucose uptake, particularly by cells gorwing in glucose-sufficient environments.

Ammonia↗
PubMed1980

Glucose phosphoenolpyruvate phosphotransferase activity and glucose uptake rate of Klebsiella aerogenes growing in chemostat culture.

Glucose-limited cultures of Klebsiella aerogenes NCTC 418 (and the supposedly identical strain NCIB 418) possessed a glucose phosphoenolpyruvate (PEP) phosphotransferase activity that varied markedly and progressively with growth rate, from more than 250 nmol min-1 (mg dry wt cells)-1 at D = 0.1 h-1 to less than 100 nmol min-1 (mg dry wt cells)-1 at D = 0.8 h-1. When relieved of the glucose limitation, substrate was used at a rate that bore no precise relationship to the cells' phosphotransferase activity. Similarly, glucose-sufficient (phosphate- or potassium-limited) cultures metabolized glucose at high rates, whereas the cells possessed only moderate glucose PEP phosphotransferase activities. These results are compared with those reported for glucose-limited cultures of Escherichia coli and for variously limited cultures of K. aerogenes. Glucose-sufficient cultures, as well as glucose-limited cultures that had been temporarily relieved of glucose limitation, excreted partially oxidized products of glucose catabolism in considerable amounts. The relevance of this 'overflow' metabolism to studies of glucose transport using [U-14C]glucose is emphasized.

Culture Media↗