Simultaneous and efficient removal of ammonium and nitrate by a novel isolated Agrobacterium tumefaciens M

A novel nitrogen removal strain M, was isolated and identified as Agrobacterium tumefaciens M. Strain M could remove 100% and 99% of 100 mg/L ammonium and nitrate mainly through assimilation, with elimination rates of 8.61 and 4.60 mg/L/h, respectively. The optimal growth and nitrogen elimination conditions were obtained by a single-factor experiment, including a shaking speed of 150 rpm, pH of 7, C/N ratio of 15, and carbon supply of sucrose (ammonium) and sodium citrate (nitrate). Key genes involved in nitrogen metabolism, including napAB, nirK, norBC, nosZ, nirBD, glnA, and nasAB, were identified in strain M. Moreover, strain M exhibited excellent nitrogen removal efficiencies higher than 90% when ammonium and nitrate coexisted. All results indicated that strain M shows great nitrogen removal potential.