Characterization and Construction of Acinetobacter calcoaceticus T32 Strain that Can Remove Ammonia Nitrogen and Mercury

Abstract

Acinetobacter calcoaceticus has been reported to be a good candidate for removing various pollutants. In this study, A. calcoaceticus T32 could remove 100% \({\text{NH}}_{4}^{ + }\)-N and 98% of total inorganic nitrogen within 48 h, with production of traces of \({\text{NO}}_{2}^{ - }\) and \({\text{NO}}_{3}^{ - }\). The gene of subunit of ammonia monooxygenase (AMO), amoA_Ac, was cloned from A. calcoaceticus. Real-time reverse transcriptase PCR showed that mRNA level of amoA_Ac was 22-fold higher when \({\text{NH}}_{4}^{ + }\) was present, and retained to normal level in the presence of 50 mg/L allylthiourea, an inhibitor of AMO. mer operon containing merT, merP and merA genes involved in mercury resistance was fused into plasmid JR20 and introduced into A. calcoaceticus T32 through bacterial conjugation, constructing A. calcoaceticus T32/JRHg, which removed 93% HgCl₂. LD₅₀ of A. calcoaceticus T32 was 6.19 × 10⁸ CFU using model with Japanese flounder, suggesting that A. calcoaceticus T32 might be environmentally friendly to treat nitrogen and mercury pollutants.