Over the past few years the relevance of nitrate respiration in microorganisms from deep-sea hydrothermal vents has become evident. In this study, we surveyed the membrane-bound nitrate reductase (Nar) encoding gene in three different deep-sea vent microbial communities from the East Pacific Rise and the Mid-Atlantic Ridge. Additionally, we tested pure cultures of vent strains for their ability to reduce nitrate and for the presence of the NarG-encoding gene in their genomes. By using the narG gene as a diagnostic marker for nitrate-reducing bacteria, we showed that nitrate reductases related to Gammaproteobacteria of the genus Marinobacter were numerically prevalent in the clone libraries derived from a black smoker and a diffuse flow vent. In contrast, NarG sequences retrieved from a community of filamentous bacteria located about 50 cm above a diffuse flow vent revealed the presence of a yet to be identified group of enzymes. 16S rRNA gene-inferred community compositions, in accordance with previous studies, showed a shift from Alpha- and Gammaproteobacteria to Epsilonproteobacteria as the vent fluids become warmer and more reducing. Based on these findings, we argue that Nar-catalyzed nitrate reduction is likely relevant in temperate and less reducing environments where Alpha- and Gammaproteobacteria are more abundant and where nitrate concentrations reflect that of background deep seawater. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.
Publication Source (Journal or Book title)
FEMS Microbiology Ecology
Pérez-Rodríguez, I., Bohnert, K., Cuebas, M., Keddis, R., & Vetriani, C. (2013). Detection and phylogenetic analysis of the membrane-bound nitrate reductase (Nar) in pure cultures and microbial communities from deep-sea hydrothermal vents. FEMS Microbiology Ecology, 86 (2), 256-267. https://doi.org/10.1111/1574-6941.12158