The obligate aerobe Streptomyces coelicolor A3(2) synthesizes three active respiratory nitrate reductases.
Streptomyces coelicolor A3(2) synthesizes three membrane-associated respiratory nitrate reductases (Nars). During aerobic growth in liquid medium the bacterium was able to reduce 50&emsp14;mM nitrate stoichiometrically to nitrite. Construction and analysis of a mutant in which all three narGHJI operons were deleted showed that it failed to reduce nitrate. Deletion of the gene encoding MoaA, which catalyses the first step in molybdenum cofactor biosynthesis, also prevented nitrate reduction, consistent with the Nars being molybdoenzymes. In contrast to the triple narGHJI mutant, the moaA mutant was also unable to use nitrate as sole nitrogen source, which indicates that the assimilatory nitrate reductases in S. coelicolor are also molybdenum-dependent. Analysis of S. coelicolor growth on solid medium demonstrated that Nar activity is present in both spores and mycelium (hypha). Development of a survival assay with the nitrate analogue chlorate revealed that wild-type S. coelicolor spores and mycelium were sensitive to chlorate after anaerobic incubation, independent of the presence of nitrate, while both the moaA and triple nar mutants were chlorate-resistant. Complementation of the triple nar mutant with the individual narGHJI operons delivered on cosmids revealed that each operon encoded an enzyme that was synthesized and active in nitrate or chlorate reduction. The data obtained from these studies allow a tentative assignment of Nar1 activity to spores, Nar2 to spores and mycelium, and Nar3 exclusively to mycelium.
Fischer
Marco
M
Institute of Biology/Microbiology, Martin-Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
Alderson
Jesse
J
Department of Molecular Microbiology, John Innes Centre, Norwich, UK.
van Keulen
Geertje
G
Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK.|Department of Molecular Microbiology, John Innes Centre, Norwich, UK.
White
Janet
J
Department of Molecular Microbiology, John Innes Centre, Norwich, UK.
Sawers
R Gary
RG
Department of Molecular Microbiology, John Innes Centre, Norwich, UK.|Institute of Biology/Microbiology, Martin-Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
D000332:Aerobiosis; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D002704:Chlorates / Q000378:metabolism; D003067:Coenzymes / Q000096:biosynthesis; D017353:Gene Deletion; D005816:Genetic Complementation Test; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D008667:Metalloproteins / Q000096:biosynthesis; D000090006:Molybdenum Cofactors; D009154:Mutation; D050901:Nitrate Reductase / Q000096:biosynthesis* / Q000235:genetics; D009566:Nitrates / Q000378:metabolism; D009876:Operon; D010100:Oxygen / Q000378:metabolism; D011621:Pteridines; D013171:Spores, Bacterial / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D048372:Streptomyces coelicolor / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
D001426:Bacterial Proteins; D002704:Chlorates; D003067:Coenzymes; D008565:Membrane Proteins; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D050901:Nitrate Reductase; D009566:Nitrates; D010100:Oxygen; D011621:Pteridines; C022261:molybdopterin