Inhibition by acetylene of conventional hydrogenase in nitrogen-fixing bacteria

Smith, Linda A.; Hill, Susan; Yates, M. G.

doi:10.1038/262209a0

Cited by 132 publications

(66 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These observations support the view (Walker & Yates, 1978) that hydrogenase synthesis in A . chroococcum is primarily repressed by carbon metabolites and that this process overrides the effects of nitrogen source discussed above.…”

Section: Discussionsupporting

confidence: 82%

“…A reason for this relationship became apparent when it was established that the nitrogenase of Azotobacter species produced H, in vivo: Brotonegoro (1974) and Smith et al (1976) showed that N,-fixing Azotobacter chroococcum evolved H, in the presence of CO and acetylene. Smith et al (1976) offered the following explanation: CO inhibited N, or acetylene reduction by nitrogenase, thus diverting electrons to ATP-dependent H, production, and CO plus acetylene inhibited the uptake hydrogenase, thus preventing recycling of H, formed by nitrogenase. This established a rationale for the apparent association between hydrogenase and nitrogenase.…”

Section: Introductionmentioning

confidence: 99%

“…Walker & Yates (1978) showed that carbon-limited continuous cultures of A . chroococcum expressed a higher hydrogenase activity than did 0,-or N,-limited cells.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Relationship Between Hydrogenase and Nitrogenase in Azotobacter chroococcum: Effect of Nitrogen Sources on Hydrogenase Activity

et al. 1980

Self Cite

View full text Add to dashboard Cite

313The effects of different nitrogen sources on the H,-uptake hydrogenase activity were studied in batch-grown and carbon-or sulphate-limited chemostat cultures of Azotobacter chroococcum. Hydrogenase activity was significantly higher in N,-fixing than in NH4+-or NO,--dependent cultures under carbon limitation or in early-stationary phase batch growth but was not influenced by the nitrogen source in sulphate-limited cultures. Hydrogenase activity developed nearly two generation times later than nitrogenase activity during the transition from NH,+-to N,-dependent growth in carbon-limited cultures. A possible explanation is that H, produced by nitrogenase induced hydrogenase synthesis. Carbonlimited N,-fixing cultures possessed higher hydrogenase activity than did sulphate-or 0,-limited cultures. It appears that carbon substrates or metabolites act as primary repressors of hydrogenase activity and that secondary effectors, such as nitrogen sources or H,, act when such repression is removed.

show abstract

Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The Relationship Between Hydrogenase and Nitrogenase in Azotobacter chroococcum: Effect of Nitrogen Sources on Hydrogenase Activity

et al. 1980

Self Cite

View full text Add to dashboard Cite

show abstract

“…Unlike in free living, N2-fixing bacteria (20), 0.10 atm C2H2 did not inhibit hydrogenase activity in R leguminosarum strain 128C53 while preventing H2 evolution from nitrogenase (Fig. 1).…”

Section: Discussionmentioning

confidence: 99%

Variation in Nitrogenase and Hydrogenase Activity of Alaska Pea Root Nodules

Bethlenfalvay¹,

Phillips²

1979

Plant Physiol.

View full text Add to dashboard Cite

Hydrogenase activity of root nodules in the symbiotic association between Pisum sativum L. and Rhizobium leguminosarum was determined by incubating unexcised nodules with tritiated H2 and measuring tissue HTO. Hydrogenase activity saturated at 0.50 millimolar Hi and was not inhibited by the presence of 0.10 atmosphere CiH2, which prevented H2 evolution from nitrogenase. Total Hi production from nitrogenase was estimated as net H2 evolution in air plus H2 exchange in 0.10 atmosphere CGH2. Although such an estimate of nitrogenase function may not be quantitatively exact, due to uncertain relationships between H2 exchange and H2 uptake activity of hydrogenase, differences observed in H2 exchange under various conditions represent an indication of changes in hydrogenase activity. Hydrogenase activity was lower in associations grown under higher photosynthetic photon flux densities and decreased relative to total H2 production by nitrogenase. Total H2 production and hydrogenase activity were maximum 28 days after planting. Thereafter, hydrogenase activity and H2 production declined, but the potential proportion of nitrogenase-produced H2 recovered by the uptake hydrogenase system increased. Of five R. Ieguminosarum strains tested two possessed hydrogenase activity. Strains which had the potential to reassimilate H2 had significantly higher rates of N2 reduction than those which did not exhibit hydrogenase activity.Reduction of C2H2 to C2H4 by nitrogenase is measured easily by gas chromatography (12). As a consequence, this assay has become a major research technique for estimating biological N2 fixation. In the process of interacting with nitrogenase, however, C2H2 inhibits ATP-dependent H2 evolution by this enzyme complex (6). The first reproducible demonstration of H2 evolution from soybean root nodules (13) apparent that a better understanding of uptake hydrogenase activity and H2 production by nitrogenase is needed to comprehend factors which affect the efficiency of N2 fixation.Whole-plant studies revealed that plant ontogeny (5) and irradiance (4) during 4 weeks of growth markedly altered the relative efficiency of N2 fixation calculated according to Schubert and Evans (18). Although those experiments demonstrated that the host legume could affect the efficiency of bacteroid functioning, there were no data to indicate whether the altered levels of H2 evolution resulted from changes in uptake hydrogenase activity or from differences in H2 production by nitrogenase. The present experiments were performed to separate the effects of ontogeny and growth irradiance on nitrogenase and hydrogenase activity in Rhizobium leguminosarum 128C53. In addition, other strains of this bacterial species were examined for hydrogenase and nitrogenase activity in vivo to determine the mechanisms underlying different N2 reduction rates which alter photosynthetic efficiency (3). MATERIALS AND METHODS

show abstract

“…Frankia, occasionally evolve hydrogen at a high rate (17). Hydrogen evolution was shown to be caused by the inhibition of uptake hydrogenase during acetylene reduction assays, first in Azotobacter (12) and later in Frankia symbioses (16,17 …”

mentioning

confidence: 99%

Acetylene, Not Ethylene, Inactivates the Uptake Hydrogenase of Actinorhizal Nodules during Acetylene Reduction Assays

Sellstedt¹,

Winship²

1990

Plant Physiol.

View full text Add to dashboard Cite

Acetylene reduction assays were shown to inactivate uptake hydrogenase activity to different extents in one Casuarina and two Alnus symbioses. Inactivation was found to be caused by C2H2 and not by C2H4. Acetylene completely inactivated the hydrogenase activity of intact root systems of Alnus incana inoculated with Frankia strain Avcll in 90 minutes, as shown by a drop in the relative efficiency of nitrogenase from 1.0 to 0.73. The hydrogenase of Frankia preparations (containing vesicles) and of cell-free extracts (not containing vesicles) from the same symbiosis was much more susceptible to acetylene inactivation. Cellfree extracts lost all hydrogenase activity after 5 minutes of exposure to acetylene. The hydrogenase activity of intact root systems of Casuarina obesa was less sensitive to acetylene than that of root systems of A. incana, since the relative efficiency of nitrogenase changed only from 1.0 to 0.95 over 90 minutes. Frankia preparations and cell-free extracts of C. obesa still retained hydrogenase activity after a 10 minute-exposure to acetylene.Alnus incana were exposed to C2H2 and/or to C2H4. Evolution of hydrogen gas from the intact nodulated root systems following exposure to ethylene or acetylene was interpreted as resulting from the inactivation of hydrogenase. The rate of hydrogen evolution was compared to the rate of acetylene reduction for the same root system to estimate the degree of hydrogenase inactivation. To assess the relative influence of host plant and Frankia strain on sensitivity to acetylene inactivation, we tested the same host plant (A. incana) with two different Frankia strains.Nodules were also homogenized to provide isolated symbiotic Frankia preparations and cell-free preparations. The hydrogen uptake activity of these preparations was assayed directly to compare the sensitivity of hydrogenase to acetylene in more exposed configurations, i.e. in the absence of host cells and metabolites. Also, the sensitivity to ethylene was tested in Frankia preparations from A. incana nodules. Symbiotic Frankia from A. incana consisted of both symbiotic vesicles and hyphae, while C. obesa preparations contained no vesicles.Unlike many symbiotic associations of Rhizobia and their legume hosts, root nodules ofFrankia symbioses rarely evolve hydrogen gas due to the activity of an uptake hydrogenase (2, 6-8, 10, 1 1). Despite the presence of an uptake hydrogenase system in most nitrogen-fixing organisms, these organisms, e.g. Frankia, occasionally evolve hydrogen at a high rate (17). Hydrogen evolution was shown to be caused by the inhibition of uptake hydrogenase during acetylene reduction assays, first in Azotobacter (12) and later in Frankia symbioses (16,17).As shown by Winship et al. (17), the uptake hydrogenase systems of Frankia symbioses vary substantially in response to acetylene reduction assays. Alnus-Frankia symbioses were most affected by acetylene reduction assays, while CasuarinaFrankia symbioses were less affected. The mechanisms and the time course of inactivation o...

show abstract

Inhibition by acetylene of conventional hydrogenase in nitrogen-fixing bacteria

Cited by 132 publications

References 10 publications

The Relationship Between Hydrogenase and Nitrogenase in Azotobacter chroococcum: Effect of Nitrogen Sources on Hydrogenase Activity

The Relationship Between Hydrogenase and Nitrogenase in Azotobacter chroococcum: Effect of Nitrogen Sources on Hydrogenase Activity

Variation in Nitrogenase and Hydrogenase Activity of Alaska Pea Root Nodules

Acetylene, Not Ethylene, Inactivates the Uptake Hydrogenase of Actinorhizal Nodules during Acetylene Reduction Assays

Contact Info

Product

Resources

About