Functional-Structural Analysis of Nitrogen-Cycle Bacteria in a Hypersaline Mat from the Omani Desert

Abstract

Potential rates of ammonia oxidation, denitrification and anammox were measured in a hypersaline microbial mat. Ammonia oxidation and denitrification had potential rates of 0.8 ± 0.4 and 2.0 ± 1.0 nmol N g⁻¹ h⁻¹, respectively, anammox was not detectable. The rate of N₂O production under anoxic conditions accounted for ca. 5% of total denitrification. Using qPCR, the ammonia-oxidation (amoA) genes of gammaproteobacteria had the highest copy number. The denitrification genes narG and nirS exhibited comparable estimates. Sequences of nirS gene were novel, whereas nirK sequences were related to sequences from the Rhizobiales group. Sequences of the nosZ gene were the most diverse and clustered with sequences from various genera. Our results demonstrate that the hypersaline mat from Oman harbors nitrifying and denitrifying bacteria with the potential to perform respective processes at detectable rates.

Keywords:

• acetylene inhibition assay
• denitrification
• functional genes
• hypersaline microbial mat
• nitrogen cycle
• quantitative PCR