Methylammonium (ammonium) uptake in a glutamine auxotroph of the cyanobacterium <i>Anabaena cycadeae</i>

Singh, Dipti; Rai, Amar; Singh, H. N.

doi:10.1016/0014-5793(85)81337-5

Cited by 20 publications

(17 citation statements)

References 18 publications

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“…Further evidence that ANR activity in soil is regulated by glutamine formed by microbial assimilation of NH' was provided by studies showing that aminotransferase inhibitors that block metabolism of glutamine inhibited ANR activity in soil treated with NO-but did not do so in the presence of MSX (Table 3). Methylammonium (CH3NH+) labeled with 14C has been used as an NH'+ analog to study the carriers involved in transport of NH' across cytoplasmic membranes, and experiments using this compound have shown that MSX inhibits transport of CH3NH' across these membranes (17)(18)(19)(20)(21)(22)(23)(24)(25).…”

mentioning

confidence: 99%

Regulation of assimilatory nitrate reductase activity in soil by microbial assimilation of ammonium.

McCarty

Bremner

1992

Proc. Natl. Acad. Sci. U.S.A.

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It is well established that assimilatory nitrate reductase (ANR) activity in soil is inhibited by ammonium (NHIt). To elucidate the mechanism of this inhibition, we studied the effect of L-methionine sulfoximine (MSX), an inhibitor of NH' assimilation by microorganisms, on assimilatory reduction of nitrate (NO-) in aerated soil slurries treated with NH:. We found that NHj strongly inhibited ANR activity in these slurries and that MSX eliminated this inhibition. We also found that MSX induced dissimilatory reduction of NO3 to NHI in soil and that the NH$ thus formed had no effect on the rate of NO -reduction. We concluded from these observations that the inhibition of ANR activity by NHj is due not to NH+ per se but to products formed by microbial assimilation of NHI4. This conclusion was supported by a study of the effects of early products of NH+ assimilation (L amino acids) on ANR activity in soil, because this study showed that the biologically active, L isomers of glutamine and asparagine strongly inhibited ANR activity, whereas the D isomers of these amino acids had little effect on ANR activity. Evidence that ANR activity is regulated by the glutamine formed by NH4: assimilation was provided by studies showing that inhibitors of glutamine metabolism (azaserine, albizziin, and aminooxyacetate) inhibited ANR activity in soil treated with NO1 but did not do so in the presence of MSX.There is international concern about the potential adverse effects of fertilizer-derived nitrate (NO-) on environmental quality and public health (1-4). This concern has stimulated research on the biological and nonbiological processes that affect the fate of NO3 in soils, and it is well established that NO-is the substrate of at least three microbial processes in soils: denitrification, assimilatory NO-reduction, and dissimilatory NO-reduction. Denitrification leads to reduction of NO-to dinitrogen (N2) and nitrous oxide (N20), whereas both assimilatory and dissimilatory NO-reduction lead to conversion of NO3 to NH'. Dissimilatory NO-reduction is not affected by NH' (5), whereas assimilatory NOj reduction is strongly inhibited-by NH' (6).It is generally assumed that assimilatory NO-reduction is a minor fate of NO-in soil compared with plant uptake, leaching, and denitrification (7-9). This assumption is based largely on studies showing that NH' is a potent inhibitor of NO-assimilation by soil microorganisms and that NH' concentrations in agricultural soils are usually greater than those required to inhibit assimilatory NO-reductase (ANR) activity (9-11). Very little information is available, however, concerning assimilatory reduction of NO-in soil and the factors affecting this process. The purpose of the work reported here was to elucidate the mechanism of inhibition of ANR in soil by NH't. MATERIALS AND METHODSThe soils used (Table 1) were surface samples (0-15 cm) of Iowa soils that had been sieved (2-mm screen) and stored (4°C) in the field-moist condition. Immediately before use in studies of assimilatory reduction o...

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confidence: 99%

Regulation of assimilatory nitrate reductase activity in soil by microbial assimilation of ammonium.

McCarty

Bremner

1992

Proc. Natl. Acad. Sci. U.S.A.

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“…is able to use these amino acids as sole N-source for their growth and GS activity is essential for them to do so 19 . Using 14 C-methylammonium as probe, an energy-dependent and NO 3 --and NH 4 + -repressible ammonium transport system, that is essential for cyclic retention of ammonia in the cells, has been characterized in several cyanobacteria 16,17,29,30 . Typically, in all cases, 14 C-methylammonium uptake shows a biphasic curve, a rapid fi rst phase of accumulation lasting 60 s followed by a slower second phase linked to 14 C-methylammonium assimilation.…”

Section: Resultsmentioning

confidence: 99%

Isolation and characterization of a Mastigocladus species capable of growth, N2-fixation and N-assimilation at elevated temperature

et al. 2007

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A Mastigocladus species was isolated from the hot spring of Jakrem (Meghalaya) India. Uptake and utilization of nitrate, nitrite, ammonium and amino acids (glutamine, asparagine, arginine, alanine) were studied in this cyanobacterium grown at different temperatures (25ºC, 45ºC). There was 2-3 fold increase in the heterocyst formation and nitrogenase activity in N-free medium at higher temperature (45ºC). Growth and uptake and assimilation of various nitrogen sources were also 2-3 fold higher at 45ºC indicating that it is a thermophile. The extent of induction and repression of nitrate uptake by NO 3¯ and NH 4 + , respectively, differed from that of nitrite. It appeared that Mastigocladus had two independent nitrate/nitrite transport systems. Nitrate reductase and nitrite reductase activitiy was not NO 3¯-inducible and ammonium or amino acids caused only partial repression. Presence of various amino acids in the media partially repressed glutamine synthetase activity. Ammonium (methylammonium) and amino acid uptake showed a biphasic pattern, was energy-dependent and the induction of uptake required de novo protein synthesis. Ammonium transport was substrate (NH 4 + ) -repressible, while the amino acid uptake was substrate inducible. When grown at 25ºC, the cyanobacterium formed maximum akinetes that remained viable upto 5 years under dry conditions.

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“…Addition of MSX 5 min after the addition of [ 14C]methylammonium caused an effect similar to that of ammonium addition, leading to an immediate efflux of 14C-label from the cells and cessation of any further uptake. The efflux caused by MSX has not been noted in other cyanobacteria (Rai et al, 1984;Singh et al, 1985;Rai & Prakasham, 1989) and may reflect the fact that unlike other cyanobacteria, Nostoc sp. ANTH metabolizes methylammonium as a nitrogen source.…”

Section: Eflect Of Msx On [ 14c]rnethylarnrnoniurn Uptake By N2-mentioning

confidence: 98%

Evidence for the occurrence of a specific methylammonium transport system in the cultured cyanobiont of the Anthoceros punctatus-Nostoc association

Prakasham¹,

N.²

1991

Journal of General Microbiology

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Methylammonium uptake and metabolism was studied in Nostoc sp. ANTH (a free-living cultured isolate from Anthoceros punctatus). Unlike other cyanobacteria, Nostoc sp. ANTH assimilated methylammonium as a fixed nitrogen source. While N2-grown Nostoc sp. ANTH cells showed ammonium transport characteristics similar to those in other cyanobacteria, a specific energy-dependent methylammonium transport was noticed in methylammonium-grown cells. Unlike methylammonium/ammonium transport in N2-grown cells, methylammonium transport in methylammonium-grown cells was neither affected by ammonium nor by L-methiOnhe-DLsulphoximine.

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Methylammonium (ammonium) uptake in a glutamine auxotroph of the cyanobacterium Anabaena cycadeae

Cited by 20 publications

References 18 publications

Regulation of assimilatory nitrate reductase activity in soil by microbial assimilation of ammonium.

Regulation of assimilatory nitrate reductase activity in soil by microbial assimilation of ammonium.

Isolation and characterization of a Mastigocladus species capable of growth, N2-fixation and N-assimilation at elevated temperature

Evidence for the occurrence of a specific methylammonium transport system in the cultured cyanobiont of the Anthoceros punctatus-Nostoc association

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