Journal
ISME JOURNAL
Volume 8, Issue 7, Pages 1510-1521Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/ismej.2013.246
Keywords
Epsilonproteobacteria; nitrate reduction; deep-sea vents; napA
Categories
Funding
- NSF [MCB 04-56676, MCB 08-43678, OCE 11-36451, OCE 03-27353]
- NIH [NIH NIGMS 5 T32 GM08339]
- NSF Graduate Research Fellowship
- Directorate For Geosciences
- Division Of Ocean Sciences [1136451] Funding Source: National Science Foundation
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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.
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