A membrane-bound nitrate reductase encoded by the narGHJI operon is responsible for anaerobic respiration in Halomonas maura |
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Authors: | Montserrat Argandoña Fernando Martínez-Checa Inmaculada Llamas Yolanda Arco Emilia Quesada Ana del Moral |
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Affiliation: | (1) Department of Microbiology, Faculty of Pharmacy, University of Granada, Campus Universitario de Cartuja s/n, 18071 Granada, Spain |
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Abstract: | The halophilic bacterium Halomonas maura is capable of anaerobic respiration on nitrates. By insertional mutagenesis with the minitransposon Tn-5 we obtained the mutant Tc62, which was incapable of anaerobic respiration on nitrates. An analysis of the regions adjacent to the transposon allowed us to characterize the membrane-bound anaerobic-respiratory nitrate reductase narGHJI gene cluster in H. maura. We identified consensus sequences for fumarate and nitrate reductase regulator (FNR)-like protein-binding sites in the promoter regions of the nar genes and consensus sequences corresponding to the NarL binding sites upstream of the nar genes. RT-PCR analysis showed that the narGHJI operon was expressed in response to anaerobic conditions when nitrate was available as electron acceptor. This membrane-bound nitrate reductase is the only enzyme responsible for anaerobic respiration on nitrate in H. maura. In this article we discuss the possible relationship between this enzyme and a dissimilatory nitrate-reduction-to-ammonia process (DNRA) in H. maura and its role in the colonization of the rhizosphere. |
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Keywords: | Halomonas Halophilic bacteria Nar genes Nitrate reductase |
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