Journal
ISME JOURNAL
Volume 5, Issue 7, Pages 1201-1212Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/ismej.2010.205
Keywords
nitrogen fixation; nifH; nitrogenase; molecular; Cape Verde; Atlantic
Categories
Funding
- Natural Environment Research Council through the UK SOLAS
- Natural Environment Research Council [NE/C507902/1]
- Gordon and Betty Moore Foundation
- NERC [NE/D006511/1, NE/D00649X/1] Funding Source: UKRI
- Natural Environment Research Council [NE/D00649X/1, NE/D006511/1, ceh010023] Funding Source: researchfish
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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
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