Nitrogenase Gene Amplicons from Global Marine Surface Waters Are Dominated by Genes of Non-Cyanobacteria
2011 (English)In: PLOS ONE, ISSN 1932-6203, Vol. 6, no 4, e19223- p.Article in journal (Refereed) Published
Cyanobacteria are thought to be the main N-2-fixing organisms (diazotrophs) in marine pelagic waters, but recent molecular analyses indicate that non-cyanobacterial diazotrophs are also present and active. Existing data are, however, restricted geographically and by limited sequencing depths. Our analysis of 79,090 nitrogenase (nifH) PCR amplicons encoding 7,468 unique proteins from surface samples (ten DNA samples and two RNA samples) collected at ten marine locations worldwide provides the first in-depth survey of a functional bacterial gene and yield insights into the composition and diversity of the nifH gene pool in marine waters. Great divergence in nifH composition was observed between sites. Cyanobacteria-like genes were most frequent among amplicons from the warmest waters, but overall the data set was dominated by nifH sequences most closely related to non-cyanobacteria. Clusters related to Alpha-, Beta-, Gamma-, and Delta-Proteobacteria were most common and showed distinct geographic distributions. Sequences related to anaerobic bacteria (nifH Cluster III) were generally rare, but preponderant in cold waters, especially in the Arctic. Although the two transcript samples were dominated by unicellular cyanobacteria, 42% of the identified non-cyanobacterial nifH clusters from the corresponding DNA samples were also detected in cDNA. The study indicates that non-cyanobacteria account for a substantial part of the nifH gene pool in marine surface waters and that these genes are at least occasionally expressed. The contribution of non-cyanobacterial diazotrophs to the global N-2 fixation budget cannot be inferred from sequence data alone, but the prevalence of non-cyanobacterial nifH genes and transcripts suggest that these bacteria are ecologically significant.
Place, publisher, year, edition, pages
2011. Vol. 6, no 4, e19223- p.
NORTH PACIFIC-OCEAN, BALTIC SEA PROPER, ATLANTIC-OCEAN, NIFH GENE, N-2-FIXING CYANOBACTERIA, CHESAPEAKE BAY, DIVERSITY, DISTRIBUTIONS, AMPLIFICATION, EXPRESSION
Biochemistry and Molecular Biology
IdentifiersURN: urn:nbn:se:kth:diva-33695DOI: 10.1371/journal.pone.0019223ISI: 000290024700104ScopusID: 2-s2.0-79955742866OAI: oai:DiVA.org:kth-33695DiVA: diva2:418603
FunderFormas, 217-2006-342Swedish Research Council, 621-205-4710Swedish Research Council, 2009-3784Swedish Research Council, 2008-1293Science for Life Laboratory - a national resource center for high-throughput molecular bioscience
QC 201105232011-05-232011-05-162011-12-06Bibliographically approved