An Oxygen-tolerant Denitrifying Strain and Its Denitrifying Processes

Abstract:

An oxygen-tolerant denitrifying strain designated as H1 was screened by the procedures of shallow shaking and continuous aeration cultures. With the aid of an nnrS-gfp fusion responsive to nitric oxide (NO) and acetylene inhibition-GC procedure, it was shown that strain H1 was able to produce NO and N2O but not N2 under denitrifying conditions. Denitrifying processes were thus determined as NO3–→NO2–→NO→N2O, with N2O as the end product. Strain H1 could denitrify under shallow shaking conditions as well as in the initial atmospheric oxygen concentration ranging from 0~21%. Denitrification processed normally under continuous aeration at the rate of 2 L air per min in a 150 mL medium, but stopped under high aeration rate as 5 L air per min. 16S rRNA gene sequence revealed that strain H1 shared 98% similarity to its closet relative Ralstonia taiwanensis, the genus where denitrifying bacteria are frequently found.