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Applied and Environmental Microbiology, December 2005, p. 7910-7919, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.7910-7919.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Diazotrophic Diversity and Distribution in the Tropical and Subtropical Atlantic Ocean

Rebecca J. Langlois, Julie LaRoche,* and Philipp A. Raab{dagger}

IFM-GEOMAR, Leibniz-Institut fuer Meereswissenschaften, Duesternbrooker Weg 20, 24105 Kiel, Germany

Received 16 March 2005/ Accepted 22 August 2005

To understand the structure of marine diazotrophic communities in the tropical and subtropical Atlantic Ocean, the molecular diversity of the nifH gene was studied by nested PCR amplification using degenerate primers, followed by cloning and sequencing. Sequences of nifH genes were amplified from environmental DNA samples collected during three cruises (November-December 2000, March 2002, and October-November 2002) covering an area between 0 to 28.3°N and 56.6 to 18.5°W. A total of 170 unique sequences were recovered from 18 stations and 23 depths. Samples from the November-December 2000 cruise contained both unicellular and filamentous cyanobacterial nifH phylotypes, as well as {gamma}-proteobacterial and cluster III sequences, so far only reported in the Pacific Ocean. In contrast, samples from the March 2002 cruise contained only phylotypes related to the uncultured group A unicellular cyanobacteria. The October-November 2002 cruise contained both filamentous and unicellular cyanobacterial and {gamma}-proteobacterial sequences. Several sequences were identical at the nucleotide level to previously described environmental sequences from the Pacific Ocean, including group A sequences. The data suggest a community shift from filamentous cyanobacteria in surface waters to unicellular cyanobacteria and/or heterotrophic bacteria in deeper waters. With one exception, filamentous cyanobacterial nifH sequences were present within temperatures ranging between 26.5 and 30°C and where nitrate was undetectable. In contrast, nonfilamentous nifH sequences were found throughout a broader temperature range, 15 to 30°C, more often in waters with temperature of <26°C, and were sometimes recovered from waters with detectable nitrate concentrations.

* Corresponding author. Mailing address: IFM-GEOMAR, Leibniz-Institut fuer Meereswissenschaften, Duesternbrooker Weg 20, 24105 Kiel, Germany. Phone: 49 431 600 4212. Fax: 49 431 600 1515. E-mail: jlaroche{at}ifm-geomar.de.

{dagger} Present address: Institute of Botany, University of Basel, Hebelstrasse 1, 4056 Basel, Switzerland.

Applied and Environmental Microbiology, December 2005, p. 7910-7919, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.7910-7919.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Langlois, R. J., Hummer, D., LaRoche, J. (2008). Abundances and Distributions of the Dominant nifH Phylotypes in the Northern Atlantic Ocean. Appl. Environ. Microbiol. 74: 1922-1931 [Abstract] [Full Text]  
  • Zehr, J. P., Bench, S. R., Mondragon, E. A., McCarren, J., DeLong, E. F. (2007). Low genomic diversity in tropical oceanic N2-fixing cyanobacteria. Proc. Natl. Acad. Sci. USA 104: 17807-17812 [Abstract] [Full Text]  


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