Mutants of Pseudomonas fluorescens deficient in dissimilatory nitrite reduction are also altered in nitric oxide reduction

Ye, R W; Arunakumari, Alahari; Averill, Bruce A.; Tiedje, James M.

doi:10.1128/jb.174.8.2560-2564.1992

Cited by 57 publications

(39 citation statements)

References 25 publications

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“…These results suggest that nitrite reduction is an obligatory requirement for nirK and nor operon expression. The coupling of nitrite reductase activity to the expression of nitrite and nitric oxide reductase has been observed in other denitrifiers (34,39).…”

Section: Discussionmentioning

confidence: 99%

Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3

et al. 1997

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Nitrite reductase catalyzes the reduction of nitrite to nitric oxide, the first step in denitrification to produce a gaseous product. We have cloned the gene nirK, which encodes the copper-type nitrite reductase from a denitrifying variant of Rhodobacter sphaeroides, strain 2.4.3. The deduced open reading frame has significant identity with other copper-type nitrite reductases. Analysis of the promoter region shows that transcription initiates 31 bases upstream of the translation start codon. The transcription initiation site is 43.5 bases downstream of a putative binding site for a transcriptional activator. Maximal expression of a nirK-lacZ construct in 2.4.3 requires both a low level of oxygen and the presence of a nitrogen oxide. nirK-lacZ expression was severely impaired in a nitrite reductase-deficient strain of 2.4.3. This suggests that nirK expression is dependent on nitrite reduction. The inability of microaerobically grown nitrite reductase-deficient cells to induce nirK-lacZ expression above basal levels in medium unamended with nitrate demonstrates that changes in oxygen concentrations are not sufficient to modulate nirK expression.The availability of fixed nitrogen is often a major factor controlling the biological productivity of ecosystems. During the cycling of nitrogen in the biosphere, a significant sink for fixed nitrogen is denitrification, the reduction of nitrate to gaseous forms of nitrogen, primarily nitrogen gas (22). Gaseous forms of nitrogen are unavailable for use by the majority of organisms. Because denitrification is a process that results in the conversion of fixed forms of nitrogen to gaseous forms, it can have a significant impact on the productivity of an ecosystem. For example, nitrate concentrations in the ocean have been found to be a major factor limiting biological productivity (19). Denitrification is the major sink for ocean nitrate, establishing a direct link between denitrification and biological productivity in the marine environment (6). This has been dramatically demonstrated in recent studies that have shown that decreases in the rate of denitrification during the last glacial maximum may have increased the productivity of the ocean enough to lower the partial pressure of carbon dioxide in the atmosphere (1, 9).Denitrification is a respiratory process in which bacteria utilize nitrate and other inorganic oxides of nitrogen as alternate electron acceptors when oxygen concentrations are limiting. In the first step of denitrification, nitrate is reduced to nitrite (12). This reaction is not unique to denitrification, however, since it occurs during ammonification and assimilatory nitrate reduction. The next step in denitrification is the reduction of nitrite to nitric oxide (NO). This reaction is catalyzed by nitrite reductase and is the defining reaction of denitrification, since it produces the first gaseous intermediate (38). Moreover, nitric oxide-producing nitrite reductases are associated only with denitrification (12). There are two classes of nitrite reductase...

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Section: Discussionmentioning

confidence: 99%

Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3

et al. 1997

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“…First, nirS: :Tn5 mutants of Pseudomonas fluorescens not only lose their nitrite reductase activity but also have a decreased NO reductase activity. At the same time the H,"O exchange pattern of mutant cells reducing "NO is drastically changed versus the wild type with nitritereducing capability ( Ye et al, 1992). Second, a putative regulatory gene, nirQ, has been identified in l?…”

Section: Discussionmentioning

confidence: 99%

Nitric oxide reductase from Pseudomonas stutzeri

Zumft

Braun

Cuypers

1994

European Journal of Biochemistry

122

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Nitric oxide (NO) reductase is an integral membrane component of the anaerobic respiratory chain of Pseudomonas stutzeri that transforms nitrate to dinitrogen (denitrification). The enzyme catalyzes the reduction of NO to nitrous oxide. The structural genes for the NO reductase complex, norC and norB, were sequenced and their organization established by primer extension and Northern blot analysis. The norCB genes encoding the cytochrome c and cytochrome b subunits of the enzyme are contiguous and transcribed as a single 2.0-kb transcript. The promoter region has a canonical recognition motif for the transcriptional activator protein Fnr, centered at -40.5 nucleotides from the initiation site of transcription. No similarity of the derived gene products to known cytochromes of b-or c-type was found in a data bank search.Post-translational processing of the two subunits was limited to the removal of the terminal methionine to leave an N-terminal serine in either subunit. The mature cytochrome c subunit (16508Da, 145 residues) is predicted to be a bitopic protein with a single membrane anchor. The mature cytochrome b subunit (53 006Da, 473 residues) is a putatively polytopic, strongly hydrophobic membrane-bound protein with 12 potential transmembrane segments. Several histidine and proline residues were identified with potentially structural andlor functional importance.Mutational inactivation of NO reductase by deletion of norB or the norCB genes affected strongly the in vivo activity of respiratory nitrite reductase (cytochrome cd,), but to a much lesser extent the expression level of this enzyme. In turn, mutational inactivation of the structural gene for cytochrome cd,, nirS, or loss of in vivo nitrite reduction by mutation of the nirT gene, encoding a presumed tetraheme cytochrome, lowered the expression level of NO reductase to 5 -20%, but hardly its catalytic activity. The cellular concentration of NO reductase increased again on restoration of nitrite reduction in the nirS: :Tn5 mutant MK202 by complementation with nirS or with the heterologous nirK gene, encoding the Cu-containing nitrite reductase from Pseudomonas aureofaciens. Thus, NO may be required as an inducer for its own reductase. Our results show that the nitrite-reducing system and the NO-reducing system are not operating independently from each other but are interlaced by activity modulation and regulation of enzyme synthesis.

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“…However, the activity of the promoter in the presence of gaseous NO was about a third that of strain PAO1. It has been reported that the in vivo activities of NIR and NOR couple with each other (Ye et al, 1992;Zumft, 1993). Deficiency in NIR activity causes low activity of NOR, and vice versa.…”

Section: No-responding Induction Of the Nosr Promotermentioning

confidence: 99%

Transcriptional regulation of the nos genes for nitrous oxide reductase in Pseudomonas aeruginosa

2003

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The genes for nitrous oxide (N 2 O) reduction, nosRZDFYL, are clustered on the chromosome of Pseudomonas aeruginosa. Promoter assays using transcriptional fusions to lacZ revealed that the structural gene for nitrous oxide reductase, nosZ, is transcribed with the upstream nosR gene. The nosR gene product is not required for the activity of the nosR promoter. A sequence similar to the consensus FNR-binding motif was found 41?5 bp upstream from the major transcriptional start point of nosR. Mutation of the motif significantly reduced the promoter activity. DNR, an FNR-related transcriptional regulator required for the expression of denitrification genes in P. aeruginosa, is necessary for the transcription of nosR, indicating that the motif is recognized by DNR. Nitrite (NO 2 2 ), nitric oxide (NO) and NO-generating reagents induced nosR promoter activity, but N 2 O did not. The NO 2 2 -induced nosR promoter activity was reduced by mutation of the NO 2 2 reductase gene. However, a low concentration of NO 2 2 induced the promoter activity in a NO reductase mutant. These results indicate that NO is the inducer molecule for transcription of the nos genes.

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Mutants of Pseudomonas fluorescens deficient in dissimilatory nitrite reduction are also altered in nitric oxide reduction

Cited by 57 publications

References 25 publications

Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3

Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3

Nitric oxide reductase from Pseudomonas stutzeri

Transcriptional regulation of the nos genes for nitrous oxide reductase in Pseudomonas aeruginosa

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