ISSN:
1432-0789
Keywords:
Knallgas bacteria
;
Soil enzymes
;
H2 oxidation kinetics
;
Uptake hydrogenase (hup)
;
Acetylene reduction assay
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary The rate of H2 release from broad beans (Vicia faba) infected with Rhizobium leguminosarum Hup- was much faster than from beans infected with the Hup+ strain. Acetylene reduction and H2 release were abolished by cutting the plants down, by incubation in darkness, or after the addition of ammonium, indicating that the H2 was released by N2-fixing bacterial symbionts. In laboratory cultures using non-sterile soil, the bean plants released H2 until an equilibrium between H2 production and H2 oxidation was reached. The H2 equilibrium concentration was higher in Hup--infected bean cultures (about 3 ppm H2 in the gas phase) than in Hup+-infected cultures (0.3 ppm H2) because of the higher H2 production. The H2 release from Hup--infected bean cultures in sterile soil did not reach equilibrium. An equilibrium occurred, if Knallgas bacteria were added. However, the equilibrium value was higher (13 ppm H2) than in non-sterile soil, which seemed to be more efficient at H2 oxidation. The Knallgas bacteria exhibited a relatively high K m for H2 (〉 1300 ppmv H2); this activity was observed in unplanted non-sterile soil, and in nonsterile soil planted with Hup+-infected beans or planted with Hup--infected beans which had been cut down before being assayed. All these soils also showed a second, low-K m (〈50 ppm) level of H2 oxidation activity, which was presumably due to abiontic soil enzymes. In contrast, only one level of activity, which had an intermediate K m (about 200 ppm H2), was observed when the soil was planted with Hup--infected beans. The origin of this activity, which was only observed in the presence of intact, H2-producing beans, is still unknown.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00335766
Permalink
