Regulation of Nitrite Stress Response in Desulfovibrio vulgaris Hildenborough, a Model Sulfate-Reducing Bacterium.
Sulfate-reducing bacteria (SRB) are sensitive to low concentrations of nitrite, and nitrite has been used to control SRB-related biofouling in oil fields. Desulfovibrio vulgaris Hildenborough, a model SRB, carries a cytochrome c-type nitrite reductase (nrfHA) that confers resistance to low concentrations of nitrite. The regulation of this nitrite reductase has not been directly examined to date. In this study, we show that DVU0621 (NrfR), a sigma54-dependent two-component system response regulator, is the positive regulator for this operon. NrfR activates the expression of the nrfHA operon in response to nitrite stress. We also show that nrfR is needed for fitness at low cell densities in the presence of nitrite because inactivation of nrfR affects the rate of nitrite reduction. We also predict and validate the binding sites for NrfR upstream of the nrfHA operon using purified NrfR in gel shift assays. We discuss possible roles for NrfR in regulating nitrate reductase genes in nitrate-utilizing Desulfovibrio spp.


OBJECTIVE
The NrfA nitrite reductase is prevalent across several bacterial phyla and required for dissimilatory nitrite reduction. However, regulation of the nrfA gene has been studied in only a few nitrate-utilizing bacteria. Here, we show that in D. vulgaris, a bacterium that does not respire nitrate, the expression of nrfHA is induced by NrfR upon nitrite stress. This is the first report of regulation of nrfA by a sigma54-dependent two-component system. Our study increases our knowledge of nitrite stress responses and possibly of the regulation of nitrate reduction in SRB.
Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
Lara
L
Rajeev
Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
Amy
A
Chen
Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
Alexey E
AE
Kazakov
Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
Eric G
EG
Luning
Department of Biochemistry, University of Missouri, Columbia, Missouri, USA.
Grant M
GM
Zane
Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
Pavel S
PS
Novichkov
Department of Biochemistry, University of Missouri, Columbia, Missouri, USA.
Judy D
JD
Wall
Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA amukhopadhyay@lbl.gov.
Aindrila
A
Mukhopadhyay
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D045263:Cytochromes a1 / Q000235:genetics / Q000378:metabolism; D003575:Cytochromes c1 / Q000235:genetics / Q000378:metabolism; D016969:Desulfovibrio vulgaris / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009565:Nitrate Reductases / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009572:Nitrite Reductases / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D010084:Oxidation-Reduction; D013431:Sulfates / Q000378:metabolism*
D001426:Bacterial Proteins; D009566:Nitrates; D013431:Sulfates; D045263:Cytochromes a1; D003575:Cytochromes c1; D009565:Nitrate Reductases; D009572:Nitrite Reductases; C054690:nitrate reductase (cytochrome)