Nitrogeniibacter mangrovi gen. nov., sp. nov., a novel anaerobic and aerobic denitrifying betaproteobacterium and reclassification of Azoarcus pumilus as Aromatoleum pumilum comb. nov.

Denitrification is a vital link in the global bio-nitrogen cycle. Here, we isolated a strain (M9-3-2(T)) that is a novel benzo[a]pyrene (BaP)-tolerant, anaerobic and aerobic denitrifying bacterium from a continuous BaP-enrichment cultured mangrove sediment. In silico comparative genomics and taxonomic analysis clearly revealed that strain M9-3-2(T) (=MCCC 1K03313(T)=JCM 32045(T)) represents a novel species of a novel genus named as Nitrogeniibacter mangrovi gen. nov., sp. nov., belonging to family Zoogloeaceae, order Rhodocyclales. In addition, the species Azoarcus pumilus is transferred into genus Aromatoleum and named Aromatoleum pumilum comb. nov. The predominant respiratory quinone of strain M9-3-2(T) was ubiquinone-8 and the major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, three unidentified phospholipids and three unidentified aminophospholipids. In this study, the capacity of strain M9-3-2(T) to eliminate nitrate was detected under anaerobic and aerobic conditions, and the removal rates of nitrate were 6.1x10(-6) mu g N/l/h/cell and 3x10(-7) mu g N/l/h/cell, respectively. Our results suggested that strain M9-3-2(T) could play an important role in the nitrogen removal regardless of the presence of oxygen in natural or/and man-made ecosystems.

Automated summary

The study isolated a novel denitrifying bacterium from mangrove sediment, which was named as a new genus called Nitrogeniibacter mangrovi. The bacterium showed the ability to remove nitrate under both anaerobic and aerobic conditions, indicating its potential importance in nitrogen removal in various ecosystems.