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Nitrogenase gene diversity and microbial community structure: a cross-system comparison
Jonathan P Zehr1, Bethany D Jenkins, Steven M Short
1Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA 95064, USA. zehrj@cats.ucsc.edu
Environmental Microbiology
|June 26, 2003
Summary
Biological nitrogen fixation, crucial for life, is performed by microbes using nitrogenase enzymes. Analyzing the nifH gene reveals diverse microbial communities in various environments, offering insights into nitrogen cycling.
Area of Science:
- Microbiology and Environmental Science
- Molecular Biology and Genomics
Background:
- Biological nitrogen fixation is a vital process for supplying fixed nitrogen to ecosystems.
- The enzyme nitrogenase, responsible for this process, is catalyzed by microorganisms and is evolutionarily conserved.
- The nifH gene, encoding a nitrogenase component, is widely used to study microbial diversity in nitrogen fixation.
Purpose of the Study:
- To analyze the diversity and distribution of nitrogen-fixing microorganisms in various environments using nifH gene sequences.
- To understand the evolutionary relationships and ecological patterns of nitrogen-fixing bacteria.
- To explore the potential for developing molecular tools for studying natural populations of diazotrophs.
Main Methods:
- Cloning and sequencing of the nifH gene from diverse environmental samples.
- Phylogenetic analysis of nifH sequences and comparison with ribosomal RNA phylogenies.
- Analysis of nifH phylotype distribution across different habitats.
Main Results:
- A vast and expanding database of nifH sequences from diverse terrestrial and aquatic environments was generated.
- nifH phylogenies revealed characteristic distribution patterns of nitrogen-fixing microorganisms in specific habitats like termite guts, soils, and oceans.
- Sequence diversity significantly exceeded that of cultivated microorganisms, with limited evidence of lateral gene transfer impacting phylogeny.
Conclusions:
- The distribution of nitrogen-fixing microorganisms is non-random and predictable based on habitat characteristics, though not solely dictated by nitrogen availability.
- Phylogenetic analysis of nifH provides a robust framework for understanding microbial communities involved in nitrogen fixation.
- Future research can leverage these findings to develop advanced molecular assays and bioinformatics tools for environmental nitrogen fixation studies.
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