title: Deep-sea hydrothermal vent Epsilonproteobacteria encode a conserved and widespread nitrate reduction pathway (Nap).
abstract: Despite the frequent isolation of nitrate-respiring Epsilonproteobacteria from deep-sea hydrothermal vents, the genes coding for the nitrate reduction pathway in these organisms have not been investigated in depth. In this study we have shown that the gene cluster coding for the periplasmic nitrate reductase complex (nap) is highly conserved in chemolithoautotrophic, nitrate-reducing Epsilonproteobacteria from deep-sea hydrothermal vents. Furthermore, we have shown that the napA gene is expressed in pure cultures of vent Epsilonproteobacteria and it is highly conserved in microbial communities collected from deep-sea vents characterized by different temperature and redox regimes. The diversity of nitrate-reducing Epsilonproteobacteria was found to be higher in moderate temperature, diffuse flow vents than in high temperature black smokers or in low temperatures, substrate-associated communities. As NapA has a high affinity for nitrate compared with the membrane-bound enzyme, its occurrence in vent Epsilonproteobacteria may represent an adaptation of these organisms to the low nitrate concentrations typically found in vent fluids. Taken together, our findings indicate that nitrate reduction is widespread in vent Epsilonproteobacteria and provide insight on alternative energy metabolism in vent microorganisms. The occurrence of the nap cluster in vent, commensal and pathogenic Epsilonproteobacteria suggests that the ability of these bacteria to respire nitrate is important in habitats as different as the deep-sea vents and the human body.
authors.affiliation: 1] Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ, USA [2] Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, USA.
authors.forename: Costantino
authors.initials: C
authors.lastname: Vetriani
authors.affiliation: 1] Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ, USA [2] Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Voordeckers
authors.affiliation: 1] Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ, USA [2] Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, USA.
authors.forename: Melitza
authors.initials: M
authors.lastname: Crespo-Medina
authors.affiliation: 1] Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ, USA [2] Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, USA.
authors.forename: Charles E
authors.initials: CE
authors.lastname: O'Brien
authors.affiliation: 1] Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ, USA [2] Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, USA [3] Institute of Marine Science - ISMAR, National Research Council of Italy, CNR, Ancona, Italy.
authors.forename: Donato
authors.initials: D
authors.lastname: Giovannelli
authors.affiliation: Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Lutz
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D017753:Ecosystem; D020565:Epsilonproteobacteria / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D060086:Hydrothermal Vents / Q000382:microbiology; D050901:Nitrate Reductase / Q000235:genetics* / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D009566:Nitrates; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D050901:Nitrate Reductase