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

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.