Nitrogen fixation and nitrogenase (nifH) expression in tropical waters of the eastern North Atlantic
- 13 January 2011
- journal article
- Published by Oxford University Press (OUP) in The ISME Journal
- Vol. 5 (7), 1201-1212
- https://doi.org/10.1038/ismej.2010.205
Abstract
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 PO43− 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 γ-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.Keywords
This publication has 71 references indexed in Scilit:
- Methodological Underestimation of Oceanic Nitrogen Fixation RatesPLOS ONE, 2010
- Metabolic streamlining in an open-ocean nitrogen-fixing cyanobacteriumNature, 2010
- The Pfam protein families databaseNucleic Acids Research, 2009
- Distribution and activity of diazotrophs in the Eastern Equatorial AtlanticEnvironmental Microbiology, 2009
- Globally Distributed Uncultivated Oceanic N 2 -Fixing Cyanobacteria Lack Oxygenic Photosystem IIScience, 2008
- Abundances and Distributions of the Dominant nifH Phylotypes in the Northern Atlantic OceanApplied and Environmental Microbiology, 2008
- Diazotrophic bacterioplankton in a coral reef lagoon: phylogeny, diel nitrogenase expression and response to phosphate enrichmentThe ISME Journal, 2007
- High rates of nitrogen fixation during an in‐situ phosphate release experiment in the Eastern Mediterranean SeaGeophysical Research Letters, 2006
- Diversity of Diazotrophic Unicellular Cyanobacteria in the Tropical North Atlantic OceanApplied and Environmental Microbiology, 2002
- Global patterns of marine nitrogen fixation and denitrificationGlobal Biogeochemical Cycles, 1997