Whole cell respiration and nitrogenase activities in Azotobacter vinelandii growing in oxygen controlled continuous culture

Post, Eduard; Kleiner, Diethelm; Oelze, J.

doi:10.1007/bf00429410

Cited by 88 publications

(82 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…(Table 2). A similar phenomenon is described by Post et al [30] for cells growing with excess oxygen. Exposing cells to an O2 shock led to a sharp increase in whole cell nitrogenase activity (Table 2).…”

Section: Nitrogenase Activity Of Cells and Extractssupporting

confidence: 83%

See 1 more Smart Citation

The catalytic activity of nitrogenase in intact Azotobacter vinelandii cells

et al. 1985

View full text Add to dashboard Cite

The influence of the growth conditions on the concentration of nitrogenase and on the nitrogenase activity, was studied in intact Azotobacter vinelandii cells. It was observed that whole cell nitrogenase activity could be enhanced in two ways. An increase of the growth rate of cell was accompanied by an increase in whole cell nitogenase activity and by an increase in the concentration of nitrogenase in the cells. The molar ratio of Fe protein: MoFe protein was 1.47 ± 0.17 and independent of the growth rate. Activity measurements in cell extracts showed that the catalytic activity of the nitrogenase proteins was independent of the growth rate of cells. The second way to increase whole cell nitrogenase activity was to expose cells to excess oxygen. Whole cells were exposed for 2.5 h to an enhanced oxygen‐input rate. After this incubation nitrogenase activity was increased without an increase in protein concentration. It is calculated that the catalytic activity of the Fe protein in these cells was 6200 nmol C2H4 formed · min−1. With these cells and with cells grown at a high growth rate, 50% of the whole cell activity is lost by preparing a cell‐free extract. It will be demonstrated that this inactivation is partly caused by the activity measurements in vitro. When dithionite was replaced by flavodoxin as electron donor, a maximal catalytic activity of 4500 nmol C2H4 formed · min −1· (mg Fe protein)−1 was measured in vitro for the Fe protein. The results are discussed in relation to the present model for nitrogenase catalysis

show abstract

Section: Nitrogenase Activity Of Cells and Extractssupporting

confidence: 83%

“…When cells have a high respiration rate, nitrogen fixation is protected by the enhanced respiration and conformational protection by Fe/S protein I1 is less important. This explains the results of Post et al [30] who report a loss of nitrogenase activity after giving a short oxygen pulse to A. vinelundii cells grown with excess oxygen.…”

Section: Discussionsupporting

confidence: 72%

The catalytic activity of nitrogenase in intact Azotobacter vinelandii cells

et al. 1985

View full text Add to dashboard Cite

show abstract

“…With few exceptions (Hochman gt Burris, 1981;Post et al, 1983;Jensen & Cox, 1983;Klugkist & Haaker, 1984) studies of the effects of 0, on N,-fixation in vivo have used either different PO, or varied shaking rates to alter the d o 2 . With heterotrophic organisms the d o 2 is dependent both on the respiratory rats and on the solution rate of 02.…”

Section: ) I S C U S S I O Nmentioning

confidence: 99%

Nitrogen Fixation by Gloeothece sp. PCC 6909: Respiration and Not Photosynthesis Supports Nitrogenase Activity in the Light

et al. 1986

View full text Add to dashboard Cite

Nitrogenase activity of suspensions of the unicellular cyanobacterium Gloeothece sp. PCC 6909 plotted against the concentration of dissolved 0, (do,) resulted in a bell-shaped curve, both in the light and in the dark, with optima of 25 or 80 ~M -O , depending on the age of the culture, At the optimum d o 2 , nitrogenase activity [typically 4 to 6 nmol C2H, (mg protein)-' min-l] was similar in the light or in the dark. Alteration of light intensity from zero to 2 klx, or addition of 3-(3,4-dichlorophenyl)-l, 1-dimethylurea (DCMU), had no effect on nitrogenase activity. At 1 klx the ADP/ATP ratio was 0.2 and showed only a marginal increase as the d o 2 was increased. However, a high level of illumination (30 klx) stimulated or inhibited nitrogenase activity, depending on the external do,, presumably as a consequence of changes in the intracellular O2 concentration; in the presence of DCMU, activity increased twofold, independent of do,.In the dark, the dependence of the rate of respiration on O2 concentration suggested the presence of three 0,-uptake systems with apparent K, values of 1 PM, 5 p~ and 25 p~. The ADP/ATP ratio under anaerobic conditions was 0.47 and showed a marked decrease as d o 2 was increased to 25 VM. A CN-insensitive respiratory activity, which neither supported nitrogenase activity nor was coupled to ATP synthesis, was associated with the system with the apparent K, of 5 p~. The dependence of the specific activity of nitrogenase on d o 2 indicated that both the high affinity ( K , 1 WM) and low affinity ( K , 25 p~) O2-uptake systems contributed ATP or reductant for N,-fixation. KCN (2.5 mM) completely inhibited nitrogenase activity in the dark and at moderate levels of illumination and d o 2 . We conclude that respiration is the major source of reductant and ATP for nitrogenase activity both in the dark and in the light, but that photosystem I can contribute ATP at very high levels of illumination.

show abstract

“…For example, it was shown with A. vinelandii growing at high dissolved oxygen concentrations that the respiratory activity does not significantly increase with an increase in the dissolved oxygen concentration (25). Moreover, cultures of A. vinelandii exhibited comparable cellular contents and nitrogenase activities in spite of considerable differences in cellular oxygen consumption (7,13).…”

mentioning

confidence: 99%