Regulation of N2 Fixation and Ammonia Assimilation in Rhodopseudomonas sphaeroides f. sp. denitrificans. Role of Glutamine

Michalski, Wojciech P.; Nicholas, D. J. D.

doi:10.1099/00221287-130-5-1069

Cited by 4 publications

(6 citation statements)

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“…2). These data support the idea that glutamine and/or a derivative of it plays an essential role in mediating the ammonium switch-off of nitrogenase, as implicated in several other systems (11,26,35 Posttranslational regulation of nitrogenase by covalent modification of dinitrogenase reductase through ADP-ribosylation has been described earlier for certain photosynthetic bacteria, and the present work demonstrates that a similar control system can function in nonphotosynthetic bacteria.…”

Section: Resultssupporting

confidence: 75%

Posttranslational regulatory system for nitrogenase activity in Azospirillum spp

Hartmann

Lowery

et al. 1989

J Bacteriol

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The mechanism for "NH4+ switch-off/on" of nitrogenase activity in Azospirillum brasilense and A. lipoferum was investigated. A [39]) has been well studied in the purple nonsulfur photosynthetic bacterium Rhodospirillum rubrum. In R. rubrum, the loss of cellular nitrogenase activity during switch-off by NH4Cl is correlated with the covalent modification and resulting inactivation of dinitrogenase reductase (13). The covalent modification consists of the ADP-ribosylation of dinitrogenase reductase at . This reaction is catalyzed by dinitrogenase reductase ADP-ribosyltransferase (DRAT) (18,19). Dinitrogenase reductase is composed of two identical subunits, and the ADP-ribosylated subunit migrates more slowly than the unmodified subunit during sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Dinitrogenase reductase-activating glycohydrolase (DRAG) catalyzes the removal of the ADP-ribose group from the inactive dinitrogenase reductase, thereby reactivating the dinitrogenase reductase (20,31,32

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Section: Resultssupporting

confidence: 75%

Posttranslational regulatory system for nitrogenase activity in Azospirillum spp

Hartmann

Lowery

et al. 1989

J Bacteriol

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“…One of the problems in assessing the regulatory effect of interstitial NH4' on nitrogenase activity in the salt marsh is that concentrations can range from 3 to 300 p.M (3,6,7,10,21,28,35), with the higher concentrations apparently occurring early in the growing season (3). Since all in situ studies in salt marshes have shown substantial rates of nitrogenase activity (26,27), microenvironments probably exist where levels of NH4' are low enough to permit N2 fixation to occur.…”

Section: Discussionmentioning

confidence: 99%

Evidence for NH4+ switch-off regulation of nitrogenase activity by bacteria in salt marsh sediments and roots of the grass Spartina alterniflora

Yoch¹,

Whiting²

1986

Appl Environ Microbiol

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The regulatory effect of NH4' on nitrogen fixation in a Sparlina alterniflora salt marsh was examined. Acetylene reduction activity (ARA) measured in situ was only partially inhibited by NH4' in both the light and dark after 2 h. In vitro analysis of bulk sediment divided into sediment particles, live and dead roots, and rhizomes showed that microbes associated with sediment and dead roots have a great potential for anaerobic C2H2 reduction, but only if amended with a carbon source such as mannose. Only live roots had significant rates of ARA without an added carbon source. In sediment, N2-fixing mannose enrichment cultures could be distinguished from those enriched by lactate in that only the latter were rapidly inhibited by NH4'. Ammonia also inhibited ARA in dead and live roots and in surface-sterilized roots. The rate of this inhibition appeared to be too rapid to be attributed to the repression and subsequent dilution of nitrogenase. The kinetic characteristics of this inhibition and its prevention in root-associated microbes by methionine sulfoximine are consistent with the N14' switch-off-switch-on mechanism of nitrogenase regulation.

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“…Michalski and Nicholas (19) observed an increase in glutamine level during ammonium addition to a nitrogen-fixing culture of Rhodopseudomonas sphaeroides f. sp. denitrificans and concluded that the increase in glutamine concentration was responsible for the loss of nitrogenase activity.…”

Section: Discussionmentioning

confidence: 99%

“…Ammonium treatment brought about a general increase in the levels of the amino acids, whereas the effect of glutamine was transient. GS, glutamine, or metabolites related to glutamine have been proposed to regulate the switch-off of nitrogenase activity in phototrophs (7,19,37,42,44). In the present study, changes in the concentrations of glutamine, glutamate, and other amino acids of glutamate-grown cultures were monitored during switch-off of nitrogenase by ammonium, darkness, glutamine, and PMS.…”

mentioning

confidence: 99%

Amino acid concentrations in Rhodospirillum rubrum during expression and switch-off of nitrogenase activity

Kanemoto¹,

Ludden²

1987

J Bacteriol

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The amino acid concentrations in the phototrophic bacterium Rhodospirillum rubrum were measured during growth under nif-repressing and nif-derepressing conditions. The effects of ammonium, glutamine, darkness, phenazine methosulfate, and the inhibitors methionine sulfoximine and azaserine on amino acid levels of cells were tested. The changes were compared to changes in whole-cell nitrogenase activity and ADP-ribosylation of dinitrogenase reductase. Glutamate was the dominant amino acid under every growth condition. Glutamine levels were equivalent when cells were grown on high-ammonia (nif-repressing) medium or glutamate (nif-derepressing) medium. Thus, glutamine is not the solitary agent that controls nif expression. No other amino acid correlated with nif expression. Glutamine concentrations rose sharply when either glutamate-grown or N-starved cells were treated with ammonia, glutamine, or azaserine. Glutamine levels showed little change upon treatment of the cells with darkness or ammonium plus methionine sulfoximine. Treatment with phenazine methosulfate resulted in a decrease in glutamine concentration. The glutamine concentration varied independently of dinitrogenase reductase ADP-ribosylation, and it is concluded that an increase in glutamine concentration is neither necessary nor sufficient to initiate the modification of dinitrogenase reductase. No other amino acid exhibited changes in concentration that correlated consistently with modification. Glutamine synthetase activity and nitrogenase activity were not coregulated under all conditions, and thus the two regulatory cascades perceive different signal(s) under at least some conditions. Nitrogenase activity in the phototrophic bacterium Rhodospirillum rubrum is regulated at the level of expression and by posttranslational modification (8,10,12,28,33, and references therein). Oxygen and fixed sources of N such as glutamine and ammonia lead to the repression of nitrogenase; when glutamate is provided as the N source, nitrogenase is expressed.The inhibition of nitrogenase activity in vivo by ammonia was first noted by Gest et al. (8). The molecular basis for the inhibition is the ADP-ribosylation of dinitrogenase reductase (the iron protein) at a specific arginyl residue (26). Enzymes that attach (14) and remove (15,23,29) the ADP-ribosyl residue have been isolated from R. rubrum and have been found under a variety of culturing conditions (14,33).Factors that lead to the loss of activity in vivo include ammonia (10, 22, 31), glutamine (22), darkness (12, 40), and phenazine methosulfate (PMS) (12,25). Cells grown on N2 or glutamate as the N source are competent to switch-off nitrogenase activity (switch-off is the term given by Zumft and Castillo [44] to the reversible, in vivo loss of nitrogenase activity), whereas cells grown on limiting-ammonia (i.e., N-starved) medium are incapable of switch-off (38). Nitrogen assimilation in R. rubrum under nif-derepressed conditions is via glutamine synthetase (GS) and glutamate synthase (GOGAT) (3,21,32,36), and ...

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Regulation of N2 Fixation and Ammonia Assimilation in Rhodopseudomonas sphaeroides f. sp. denitrificans. Role of Glutamine

Abstract: Glutamine is shown to be the effector compound for the regulation of both nitrogenase and glutamine synthetase activities in Rhodopseudomonas sphaeroides f. sp. denitr$cans.

Cited by 4 publications

References 44 publications

Posttranslational regulatory system for nitrogenase activity in Azospirillum spp

Posttranslational regulatory system for nitrogenase activity in Azospirillum spp

Evidence for NH4+ switch-off regulation of nitrogenase activity by bacteria in salt marsh sediments and roots of the grass Spartina alterniflora

Amino acid concentrations in Rhodospirillum rubrum during expression and switch-off of nitrogenase activity

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