A new paper in the ISME Journal describes new diazotrophic organisms from oxygen-poor waters off the coastal upwelling system in Peru. Researchers from the GEOMAR Helmholtz Centre for Ocean Research and the University of Kiel have sampled DNA and RNA in these waters and designed new nifH gene probes to quantify the abundance and characterize the diversity of diazotrophic microorganims.
These researchers have found a wide range of diazotrophs inhabiting oxygen-poor waters. Remarkably, they found two new nifH clades coinciding with low oxygen and high phosphate waters, conditions which seem ideal for a high N2-fixing activity. A high diversity of proteobacterial diazotrophs was also found. Moreover, N2 fixation rates were enhanced by the addition of glucose, confirming the presence of active heterotrophic diazotrophs.
These findings suggest that (1) N2 fixation needs to be investigated in "unexpected" areas, such as high latitudes and deep basins, but also (2) new probes need to be designed, as limiting nifH analysis to the "classical" probes (UCYN-A-B-C, Trichodesmium, heterocystous cyanobacteria, and gamma-proteobacteria) likely underestimates the real diversity and abundance of diazotrophs.
Check the full paper here.
In the DIADOM project we will investigate deep-ocean diazotrophs in the waters of the SW Pacific Ocean. Keep updated for more results :)
Mar
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