Identification of two new denitrifying strains of Rhodobacter sphaeroides

Michalski, Wojciech P.

doi:10.1016/0378-1097(88)90368-0

Cited by 12 publications

(23 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

Section: Resultsmentioning

confidence: 99%

“…R. sphaeroides 2.4.3 (ATCC 17025) has been previously shown to grow anaerobically with nitrate and produce nitrogen gas (20). It has also been shown to contain a copper-type nitrite reductase (20). To isolate the gene encoding nitrite reductase, nirK, oligonucleotide primers were designed with the assumption that amino acids required for ligating the copper centers would be highly conserved (11).…”

Section: Resultsmentioning

confidence: 99%

“…Most strains are capable of using dimethyl sulfoxide as an alternative terminal electron acceptor (21). Several strains, including 2.4.3, that grow anaerobically with nitrate as a terminal electron acceptor have also been described (20). All have been shown to contain a copper-type nitrite reductase.…”

mentioning

confidence: 99%

See 2 more Smart Citations

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

et al. 1997

View full text Add to dashboard Cite

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...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 1997

View full text Add to dashboard Cite

show abstract

“…The lack of oxygen in fully anaerobic cultures should physiologically mimic the deletion of the cbb 3 -type cytochrome oxidase, thus providing an explanation of why there is limited expression of nirK under anaerobic, dark conditions. However, R. sphaeroides 2.4.3 has been reported to reduce nitrite when cultured under anaerobic light conditions (27). This raises the question of why nirK is expressed anaerobically in the presence of light, but not in its absence.…”

Section: Discussionmentioning

confidence: 99%

“…Rhodobacter sphaeroides strain 2.4.3 is a photosynthetic bacterium capable of dissimilatory reduction of nitrogen oxides under anaerobic conditions (27). Two essential enzymes in this process are nitrite reductase (Nir) and nitric oxide reductase (Nor), encoded by the nirK gene and norCBQD operon, respectively.…”

mentioning

confidence: 99%

Involvement of the PrrB/PrrA Two-Component System in Nitrite Respiration in Rhodobacter sphaeroides 2.4.3: Evidence for Transcriptional Regulation

et al. 2002

View full text Add to dashboard Cite

Rhodobacter sphaeroides strain 2.4.3 is capable of diverse metabolic lifestyles, including denitrification. The regulation of many Rhodobacter genes involved in redox processes is controlled, in part, by the PrrBA two-component sensor-regulator system, where PrrB serves as the sensor kinase and PrrA is the response regulator. Four strains of 2.4.3 carrying mutations within the prrB gene were isolated in a screen for mutants unable to grow anaerobically on medium containing nitrite. Studies revealed that the expression of nirK, the structural gene encoding nitrite reductase, in these strains was significantly decreased compared to its expression in 2.4.3. Disruption of prrA also eliminated the ability to grow both photosynthetically and anaerobically in the dark on nitrite-amended medium. Complementation with prrA restored the wild-type phenotype. The PrrA strain exhibited a severe decrease in both nitrite reductase activity and expression of a nirK-lacZ fusion. Nitrite reductase activity in the PrrA strain could be restored to wild-type levels by using nirK expressed from a heterologous promoter, suggesting that the loss of nitrite reductase activity in the PrrA and PrrB mutants was not due to problems with enzyme assembly or the supply of reductant. Inactivation of prrA had no effect on the expression of the gene encoding NnrR, a transcriptional activator required for the expression of nirK. Inactivation of ccoN, part of the cbb 3 -type cytochrome oxidase shown to regulate the kinase activity of PrrB, also caused a significant decrease in both nirK expression and Nir activity. This was unexpected, since PrrA-P accumulates in the ccoN strain. Together, these results demonstrate that PrrBA plays an essential role in the regulation of nirK.

show abstract

Plasmid content and localization of the genes encoding the denitrification enzymes in two strains of Rhodobacter sphaeroides

Schwintner¹

1998

FEMS Microbiology Letters

View full text Add to dashboard Cite

Plasmid content and localization of the genes encoding the reductases of the denitrification pathway were determined in the photosynthetic bacterium Rhodobacter sphaeroides forma sp. denitrificans by transverse alternating-field electrophoresis (TAFE) and hybridization with digoxigenin-labeled homologous probes. Two large plasmids of 102 and 115 kb were found. The genes encoding the various reductases are not clustered on a single genetic unit. The nap locus (localized with a napA probe), the nirK gene and the norCB genes encoding the nitrate, nitrite and nitric oxide reductases, respectively, were found on different AseI and SnaBI digested chromosomal DNA fragments, whereas the nos locus (localized with a nosZ probe), encoding the nitrous oxide reductase, was identified on the 115-kb plasmid. Furthermore, the genes encoding two proteins of unknown function, one periplasmic and the other cytoplasmic, but whose synthesis is highly induced by nitrate, were found on a different chromosomal fragment. For comparison, the same experiments were carried out on the well-characterized strain Rhodobacter sphaeroides 2.4.1. z

show abstract

Identification of two new denitrifying strains of Rhodobacter sphaeroides

Cited by 12 publications

References 5 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

Involvement of the PrrB/PrrA Two-Component System in Nitrite Respiration in Rhodobacter sphaeroides 2.4.3: Evidence for Transcriptional Regulation

Plasmid content and localization of the genes encoding the denitrification enzymes in two strains of Rhodobacter sphaeroides

Contact Info

Product

Resources

About