A global census of nitrogenase diversity.
John Christian Gaby1, Daniel H Buckley
1Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA.
Environmental Microbiology
|May 4, 2011
Summary
Global nitrogen-fixing microorganism diversity is largely unknown, with many species yet to be discovered. Current data shows uneven distribution across environments and phylogenetic groups, highlighting areas for future research.
Area of Science:
- Microbiology
- Environmental Science
- Genomics
Background:
- Nitrogen-fixing microorganisms, or diazotrophs, are crucial for global nutrient cycling.
- Understanding their diversity is essential for ecological and agricultural applications.
- Previous assessments of diazotroph diversity have been limited in scope.
Purpose of the Study:
- To comprehensively assess the global diversity of nitrogen-fixing microorganisms.
- To identify under-explored phylogenetic groups and environments for diazotrophs.
- To characterize the distribution and abundance of diazotrophs.
Main Methods:
- Construction and analysis of a large, aligned database of 16,989 nitrogenase reductase (nifH) gene sequences.
- Phylogenetic analysis of nifH sequences to determine microbial diversity.
- Frequency distribution analysis of operational taxonomic units (OTUs).
Main Results:
- The global diversity of diazotrophs is significantly underestimated, with numerous undiscovered organisms.
- Diversity is unevenly distributed across phylogenetic lineages and environments.
- Soils exhibited the highest nifH sequence diversity; Cluster III (obligate anaerobes) showed the greatest lineage diversity but was least sampled.
- Dominant diazotrophs belong to Cyanobacteria and Proteobacteria, with some lacking isolated representatives.
Conclusions:
- Significant gaps exist in our knowledge of diazotroph diversity.
- Future research should focus on under-sampled phylogenetic groups and environments, particularly Cluster III and diverse soil communities.
- The findings provide a roadmap for future exploration of microbial diversity and function.
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