Isolation and characteristics of two heterotrophic nitrifying and aerobic denitrifying bacteria, Achromobacter sp. strain HNDS-1 and Enterobacter sp. strain HNDS-6

In order to solve nitrogen pollution in environmental water, two heterotrophic nitrifying and aerobic denitrifying strains isolated from acid paddy soil were identified as Achromobacter sp. strain HNDS-1 and Enterobacter sp. strain HNDS-6 respectively. Strain HNDS-1 and strain HNDS-6 exhibited amazing ability to nitrogen removal. When (NH4)(2)SO4, KNO3, NaNO2 were used as nitrogen resource respectively, the NH4+-N, NO3- -N, NO2- -N removal efficiencies of strain HNDS-1 were 93.31%, 89.47%, and 100% respectively, while those of strain HNDS6 were 82.39%, 96.92%, and 100%. And both of them could remove mixed nitrogen effectively in low C/N (C/ N = 5). Strain HNDS-1 could remove 76.86% NH4+-N and 75.13% NO3- -N. And strain HNDS-6 can remove 65.07% NH4+-N and 78.21% NO3(-) -N. A putative ammonia monooxygenase, nitrite reductase, nitrate reductase, assimilatory nitrate reductase, nitrate/nitrite transport protein and nitric oxide reductase of strain HNDS-1, while hydroxylamine reductase, nitrite reductase, nitrate reductase, assimilatory nitrate reductase, nitrate/nitrite transport protein, and nitric oxide reductase of strain HNDS-6 were identified by genomic analysis. DNA-SIP analysis showed that genes Nxr, narG, nirK, norB, nosZ were involved in nitrogen removal pathway, which indicates that the denitrification pathway of strain HNDS-1 and strain HNDS-6 was NO3- -> NO2- -> NO -> N2O -> N-2 during NH4+ -> N removal process. And the nitrification pathway of strain HNDS-1 and strain HNDS-6 was NO2- -> NO3- , but the nitrification pathway of NH4+ -> NO2- needs further studies.

Automated summary

To solve nitrogen pollution in environmental water, two strains, Achromobacter sp. strain HNDS-1 and Enterobacter sp. strain HNDS-6, were isolated from acid paddy soil and identified as heterotrophic nitrifying and aerobic denitrifying strains. Both strains showed remarkable ability in removing nitrogen, with strain HNDS-1 achieving removal efficiencies of 93.31% for NH4+-N, 89.47% for NO3--N, and 100% for NO2--N when using different nitrogen resources. Genomic analysis identified key enzymes and transport proteins involved in nitrogen removal pathways. Further analysis revealed denitrification pathways of NO3-- > NO2-- > NO -> N2O -> N-2 for strain HNDS-1 and strain HNDS-6, while the nitrification pathway of NH4+ -> NO2- requires further investigation.