Isolation and characterization of a denitrifying Acinetobacter baumannii H1 using NO2--N as nitrogen source from shrimp farming ponds

Abstract

Recent studies have revealed that the use of denitrifying bacteria is an alternative to eliminate nitrite accumulation in the wastewaters. However, no information is available about Acinetobacter species as a denitrifying agent for reducing nitrite in aquaculture. In the present study, a potential denitrifying strain H1 was isolated from shrimp farming ponds using nitrite as nitrogen source, which displayed almost complete nitrite removal. It was initially identified as Acinetobacter baumannii using API identification kits, and confirmed to be A. baumannii strain (GenBank accession no. JF751054) by phylogenetic analysis. Three key denitrification genes nirS, norB and nirK were detected from strain H1 by PCR amplification. In addition, it was demonstrated to be safe for mammals and giant freshwater prawns, and showed in vitro high nitrite removal activities at a wide range of initial pH 5-9 and 15 to 35°C with a final cell density of 105-107 cfu/ml. To the best of our knowledge, this is the first report on a promising denitrifying A. baumannii strain from shrimp farming ponds. Key words: Characterization, nitrite removal, Acinetobacter baumannii, shrimp farming.