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Nitrogen fixation and nitrogenase (nifH) expression in tropical waters of the eastern North Atlantic

Turk, Kendra A.; Rees, Andrew P.; Zehr, Jonathan P.; Pereira, Nicole; Swift, Paul; Shelley, Rachel; Lohan, Maeve; Woodward, E. Malcolm S.; Gilbert, Jack. 2011 Nitrogen fixation and nitrogenase (nifH) expression in tropical waters of the eastern North Atlantic. ISME Journal, 5 (7). 1201-1212. 10.1038/ismej.2010.205

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Abstract/Summary

Expression of nifH in 28 surface water samples collected during fall 2007 from six stations in the vicinity of the Cape Verde Islands (north-east Atlantic) was examined using reverse transcription-polymerase chain reaction (RT-PCR)-based clone libraries and quantitative RT-PCR (RT-qPCR) analysis of seven diazotrophic phylotypes. Biological nitrogen fixation (BNF) rates and nutrient concentrations were determined for these stations, which were selected based on a range in surface chlorophyll concentrations to target a gradient of primary productivity. BNF rates greater than 6 nmolN l(-1) h(-1) were measured at two of the near-shore stations where high concentrations of Fe and PO(4)(3-) were also measured. Six hundred and five nifH transcripts were amplified by RT-PCR, of which 76% are described by six operational taxonomic units, including Trichodesmium and the uncultivated UCYN-A, and four non-cyanobacterial diazotrophs that clustered with uncultivated Proteobacteria. Although all five cyanobacterial phylotypes quantified in RT-qPCR assays were detected at different stations in this study, UCYN-A contributed most significantly to the pool of nifH transcripts in both coastal and oligotrophic waters. A comparison of results from RT-PCR clone libraries and RT-qPCR indicated that a gamma-proteobacterial phylotype was preferentially amplified in clone libraries, which underscores the need to use caution interpreting clone-library-based nifH studies, especially when considering the importance of uncultivated proteobacterial diazotrophs. The ISME Journal (2011) 5, 1201-1212; doi:10.1038/ismej.2010.205; published online 13 January 2011 Subject Category: microbial ecology and functional diversity of natural habitats

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1038/ismej.2010.205
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry
CEH Sections: Hails
ISSN: 1751-7362
Additional Keywords: nitrogen fixation, nifH, nitrogenase, molecular, Cape Verde, Atlantic
NORA Subject Terms: Biology and Microbiology
Ecology and Environment
Date made live: 28 Feb 2012 12:27
URI: http://nora.nerc.ac.uk/id/eprint/16778

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