Ammonium inhibition of nitrogenase activity in Herbaspirillum seropedicae

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Journal of Bacteriology; (USA)

OSTI ID:6995371

Fu, H; Burris, R H ^[1]

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1. Univ. of Wisconsin, Madison (USA)

The effect of oxygen, ammonium ion, and amino acids on nitrogenase activity in the root-associated N{sub 2}-fixing bacterium Herbaspirillum seropedicae was investigated in comparison with Azospirillum spp. and Rhodospirillum rubrum. H. seropedicae is microaerophilic, and its optimal dissolved oxygen level is from 0.04 to 0.2 kPa for dinitrogen fixation but higher when it is supplied with fixed nitrogen. No nitrogenase activity was detected when the dissolved O{sub 2} level corresponded to 4.0 kPa. Ammonium, a product of the nitrogenase reaction, reversible inhibited nitrogenase activity when added to derepressed cell cultures. However, the inhibition of nitrogenase activity was only partial even with concentrations of ammonium chloride as high as 20 mM. Amides such as glutamine and asparagine partially inhibited nitrogenase activity, but glutamate did not. Nitrogenase in crude extracts prepared from ammonium-inhibited cells showed activity as high as in extracts from N{sub 2}-fixing cells. The pattern of the dinitrogenase and the dinitrogenase reductase revealed by the immunoblotting technique did not change upon ammonium chloride treatment of cells in vivo. No homologous sequences were detected with the draT-draG probe from Azospirillum lipoferum. There is no clear evidence that ADP-ribosylation of the dinitrogenase reductase is involved in the ammonium inhibition of H. seropedicae. The uncoupler carbonyl cyanide m-chlorophenylhydrazone decreased the intracellular ATP concentration and inhibited the nitrogenase activity of whole cells. The ATP pool was significantly disturbed when cultures were treated with ammonium in vivo.

• DOE Contract Number: FG02-87ER13707
• OSTI ID: 6995371
• Journal Information: Journal of Bacteriology; (USA), Vol. 171:6; ISSN 0021-9193
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
AMMONIUM COMPOUNDS
TOXICITY
NITROGENASE
BIOCHEMICAL REACTION KINETICS
RHIZOBIUM
ENZYME ACTIVITY
AMINO ACIDS
INHIBITION
OXYGEN
RHODOSPIRILLUM
BACTERIA
CARBOXYLIC ACIDS
ELEMENTS
ENZYMES
KINETICS
MICROORGANISMS
NITRO-GROUP DEHYDROGENASES
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
REACTION KINETICS
550200* - Biochemistry