In:
Biochemistry and Cell Biology, Canadian Science Publishing, Vol. 64, No. 4 ( 1986-04-01), p. 328-336
Abstract:
The washed cells of Rhodopseudomonas sphaeroides f.sp. denitrificans developed a Δp of about −175 to −200 mV during denitrification in the dark and −200 to −245 mV in the light. With NO 2 − as the terminal acceptor, Δp was less than with NO 3 − , N 2 O, or O 2 . The values of Δψ in the dark were about −150 mV for NO 3 − and N 2 O and −140 mV for NO 2 − . During photodenitrification with NO 3 − , NO 2 − , or N 2 O or respiration to O 2 in light, Δψ ranged between −152 and −167 mV. Like Δψ, the ΔpH was higher in light than in the dark, resulting in a 20- to 30-mV increase in Δp during illumination with NO 3 − , NO 2 − , or N 2 O as the acceptor. Both ΔpH and Δψ were reduced at higher pH values (≥ 7.5). Changes in pH in response to O 2 in the light were less than those in the dark, indicating light inhibition of O 2 respiration. The cells maintained a reasonably high Δp without addition of a substrate or when inhibitors were used; the cells retained a fairly high Δψ even in the presence of an inhibitor. However, ΔpH was appreciably lowered and in some cases it was almost abolished when either KCN, rotenone, NaN 3 , carbonyl cyanide m-chlorophenylhydrazone (CCCP), 2,4-dinitrophenol, N,N′-dicyclohexylcarbodiimide, antimycin A, or 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO) was used. The combination of an uncoupler (e.g., CCCP) and an electron transport effector (e.g., antimycin A) further reduced the ΔpH. Antimycin A and HOQNO were more effective in inhibiting photosynthetic electron transport to NO 3 − , NO 2 − , N 2 O, or O 2 than the dark respiration to these substrates. Dibromomethylisopropyl-p-benzoquinone, a quinone antagonist, markedly reduced ΔpH in light with NO 3 − , NO 2 − , N 2 O, or O 2 as the terminal acceptor, indicating that photosynthetically generated electrons are used for denitrification in this bacterium.
Type of Medium:
Online Resource
ISSN:
0829-8211
,
1208-6002
Language:
English
Publisher:
Canadian Science Publishing
Publication Date:
1986
SSG:
12
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