Genetic basis for denitrification in Ensifer meliloti
Maria J Torres, Maria I Rubia, Teodoro Coba de la Peña
1Estación Experimental del Zaidin, Consejo Superior de Investigaciones Científicas (CSIC), P,O, Box 419, 18080 Granada, Spain. mdelgado@eez.csic.es.
BMC Microbiology
|June 4, 2014
Summary
Ensifer meliloti denitrification genes napA, nirK, norC, and nosZ are crucial for nitrate respiration and enzyme expression. These genes are involved in the bacterium
Area of Science:
- Microbiology
- Environmental Science
Background:
- Denitrification is a microbial process reducing nitrate to gases like N2O, a greenhouse gas.
- Legumes may contribute to N2O production via nitrogen-rich residues or denitrifying rhizobia.
- Limited data exist on N2O production by endosymbiotic bacteria in legumes.
Purpose of the Study:
- Investigate the role of denitrification genes in Ensifer meliloti.
- Determine the function of nap, nirK, nor, and nos genes in E. meliloti.
- Clarify E. meliloti's nitrate respiration capabilities.
Main Methods:
- Genome analysis of Ensifer meliloti 1021 to identify denitrification genes.
- Construction and analysis of nap, nirK, norC, and nosZ mutant strains.
- Assessment of bacterial growth using nitrate as a respiratory substrate under varying oxygen conditions.
Main Results:
- Mutant strains lacking nap, nirK, and norC showed impaired nitrate respiration.
- The nosZ gene was not essential for growth on nitrate.
- Maximal expression of napA, nirK, norC, and nosZ genes occurred under anoxic conditions with nitrate.
Conclusions:
- Ensifer meliloti napA, nirK, norC, and nosZ genes are essential for nitrate respiration and denitrification enzyme expression.
- This study expands the known functions of denitrification genes in rhizobia.
- E. meliloti's inability to grow under initial anoxic conditions is not due to defects in these denitrification genes.
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