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Appl. Environ. Microbiol., Jul 1995, 2527-2532, Vol 61, No. 7
JP Zehr, M Mellon, S Braun, W Litaker, T Steppe and HW Paerl
The diversity of nitrogenase genes in a marine cyanobacterial mat was
investigated through amplification of a fragment of nifH, which encodes the
Fe protein of the nitrogenase complex. The amplified nifH products were
characterized by DNA sequencing and were compared with the sequences of
nitrogenase genes from cultivated organisms. Phylogenetic analysis showed
that similar organisms clustered together, with the exception that
anaerobic bacteria clustered together, even though they represented
firmicutes, (delta)-proteobacteria, and (gamma)-proteobacteria. Mat nifH
sequences were most closely related to those of the anaerobes, with a few
being most closely related to the cluster of (gamma)-proteobacteria
containing Klebsiella and Azotobacter species. No cyanobacterial nifH
sequences were found from the mat collected in November when Microcoleus
chthonoplastes was the dominant cyanobacterium, but sequences closely
related to the cyanobacterium Lyngbya lagerheimeii were found during
summer, when a Lyngbya strain was dominant. The results indicate that there
is a high diversity of heterotrophic nitrogen-fixing organisms in marine
cyanobacterial mats.
Copyright © 1995, American Society for Microbiology
Diversity of Heterotrophic Nitrogen Fixation Genes in a Marine Cyanobacterial Mat
Department of Biology MRC, Rensselaer Polytechnic Institute, Troy, New York 12180; Program in Molecular Biology and Biotechnology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina 27514; and Institute of Marine Sciences, University of North Carolina-Chapel Hill, Morehead City, North Carolina 28557
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