Characteristics and Mechanism of Heterotrophic Nitrification/Aerobic Denitrification in the Marine Tritonibacter mobilis HN1

Abstract

This work aimed to reveal the heterotrophic nitrification and aerobic denitrification activities in a salt-tolerant strain, Tritonibacter mobile HN1, isolated from mariculture sludge by using a pure culture method. Strain HN1 showed the removal rates of ammonia, nitrite, nitrate, and total nitrogen of 98.22%, 100%, 95.71%, and 86.63%, respectively, with the carbon source of sodium citrate or sodium succinate, ratio of carbon to nitrogen of 15, salinity of 3%, temperature of 30 °C, shaking speed of 120 rpm, and pH of 8. The genes of narG, narH, narI, nirS, norB, norC, nosZ, glnA, and GltB were found in the genome sequence of strain HN1, confirming the pathways of nitrogen assimilation, heterotrophic nitrification, and aerobic denitrification. In addition, two nitrifying genes, amo and nap, were missing in the genome of Tritonibacter mobile HN1, indicating that HN1 may have novel genes for this function. This study showed that HN1 had the potential to remove nitrogen contaminants in saline environments and was the first Tritonibacter mobilis strain with heterotrophic nitrification and aerobic denitrification capabilities.