ISSN:
1432-072X
Keywords:
Denitrification
;
Proton translocation
;
Photosynthesis
;
Rhodopseudomonas sphaeroides f. denitrificans
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Proton translocation during the reduction of NO 3 - , NO 2 - , N2O and O2, with endogenous substrates, in washed cells of Rhodopseudomonas sphaeroides f. denitrificans was investigated by an oxidant pulse method. On adding NO 2 - to washed cells, anaerobically in the dark, an alkalinization occurred in the reaction mixture followed by acidification. When NO 3 - , N2O or O2 was added to cells in the dark or with these compounds and NO 2 - in light an acidification only was observed. Proton translocation was inhibited by carbonyl cyanide-m-chlorophenyl hydrazone. Valinomycin treated cells produced acid in response to the addition of either NO 3 - , NO 2 - , N2O or O2. The proton extrusion stoichiometry ( $$\vec H^ + /2e^ - $$ ratios) in illuminated cells were as follows: NO 3 - →0.5N2, 4.82; NO 2 - →0.5N2, 5.43; N2O→N2, 6.20; and O2→H2O, 6.43. In the dark the comparable values were 3.99, 4.10, 4.17 and 3.95. Thus, illuminated cells produced higher $$\vec H^ + /2e^ - $$ values than those in the dark, indicating a close link between photosynthesis and denitrification in the generation of proton gradients across the bacterial cell membranes. When reduced benzyl viologen was the electron donor in the presence of 1 mM N-ethylmaleimide and 0.5 mM 2-n-heptyl-4-hydroxyquinoline-N-oxide in the dark, the addition of either NO 3 - , NO 2 - or N2O to washed cells resulted in a rapid alkalinization of the reaction mixture. The stoichiometries for proton consumption, $$\vec H^ + /2e^ - $$ ratios without a permeant ion were NO 3 - →NO 2 - ,-1.95; NO 2 - →0.5 N2O,-3.03 and N2O→N2,-2.02. The data indicate that these reductions occur on the periplasmic side of the cytoplasmic membrane.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00446978
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