Display Settings:

Format

Send to:

Choose Destination
See comment in PubMed Commons below
Appl Environ Microbiol. 2004 Feb;70(2):765-70.

N2 fixation by unicellular bacterioplankton from the Atlantic and Pacific oceans: phylogeny and in situ rates.

Author information

  • 1Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794-5000, USA. lfalcon@sfsu.edu

Abstract

N2-fixing proteobacteria (alpha and gamma) and unicellular cyanobacteria are common in both the tropical North Atlantic and Pacific oceans. In near-surface waters proteobacterial nifH transcripts were present during both night and day while unicellular cyanobacterial nifH transcripts were present during the nighttime only, suggesting separation of N2 fixation and photosynthesis by unicellular cyanobacteria. Phylogenetic relationships among unicellular cyanobacteria from both oceans were determined after sequencing of a conserved region of 16S ribosomal DNA (rDNA) of cyanobacteria, and results showed that they clustered together, regardless of the ocean of origin. However, sequencing of nifH transcripts of unicellular cyanobacteria from both oceans showed that they clustered separately. This suggests that unicellular cyanobacteria from the tropical North Atlantic and subtropical North Pacific share a common ancestry (16S rDNA) and that potential unicellular N2 fixers have diverged (nifH). N2 fixation rates for unicellular bacterioplankton (including small cyanobacteria) from both oceans were determined in situ according to the acetylene reduction and 15N2 protocols. The results showed that rates of fixation by bacterioplankton can be almost as high as those of fixation by the colonial N2-fixing marine cyanobacteria Trichodesmium spp. in the tropical North Atlantic but that rates are much lower in the subtropical North Pacific.

PMID:
14766553
[PubMed - indexed for MEDLINE]
PMCID:
PMC348867
Free PMC Article

Images from this publication.See all images (4)Free text

FIG. 1.
FIG. 2.
FIG. 3.
FIG. 4.
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk