Detection and diversity of nitrifying and denitrifying functional genes in coastal aquaculture

Nucleic acid methods based on sequencing of clone libraries provide sequence and the phylogenetic information of an individual clone. In the present study, ammonia monooxygenase (amoA), nitrite-oxido-reductase(norB), nitrite reductase (nirS) and nitrous oxide reductase (nosZ) genes are chosen to detect nitrifiers and denitrifiers in coastal aquaculture using gene-specific primers. The abundance of these functional genes revealed the presence of nitrifying and denitrifying organisms in coastal aquaculture. Nitrifying and denitrifying communities were analyzed by parallel DNA extractions and clone library construction for amoA, norB, nirS and nosZ obtained from coastal aquaculture soil. Amino acids in parts of the amoA, norB, nirS and nosZ encoded proteins were aligned to know conserved amino acid residues. The amoA genes exhibited 81–82% identity to Nitrosomonas europaea, Nitrosococcus mobilis and Nitrosomonas eutropha which were also similar to particulate methane monooxygenase (pmoA) gene sequences. The norB genes are closely affiliated with Nitrobacter winogradskyi and other uncultured beta-proteobacteria. The nosZ genes exhibited 78–82% identity with Marinobacter sp. and other uncultured denitrifying gamma-proteobacteria. The present study could be useful for making bioremediation strategy for nitrogenous metabolites and understanding of nitrogen fluxes generated through these two functional groups in coastal shrimp aquaculture.