CHARACTERIZATION OF AQUATIC NITRIFYING BACTERIUM B. cereus PB45 AND STUDY OF ITS napA AND hao GENETIC POTENTIAL IN WATER QUALITY MANAGEMENT  

Nitrogen pollution has been a serious problem for aquatic animals, aquaculture industry and ecosystem. A bacterial isolate PB45 was isolated from intensive shrimp culture pond and its nitrification capability was studied. On the basis of morphological characteristics, FAME and 16S rDNA gene sequence analysis, strain PB45 was identified as Bacillus cereus PB45. B. cereus PB45 has the potential to remove   from the ammonia, from the nitrate and  from nitrite at the rates of 1.8 , 0.026   and 3.77   respectively. The optimum pH, temperature and dissolved oxygen for the highest nitrification process of the PB45 were 8.0, 30 °C and 6.68  (200 rpm) respectively. The experimental organisms could express periplasmic nitrate reductase (napA), hydroxylamine oxidase (hao) and nitrite reductase (nirS) which are essential to complete heterotrophic nitrification and aerobic denitrification process. By PCR, both napA, hao and nirS genes were amplified in B. cereus PB45. Removal of ,  and   in open base wastewater system were achieved by 98.73%, 99.31% and 99.92% by B. cereus PB45. This result indicated that B. cereus PB45 has the prospect for future full-scale application in commercial aquaculture industry for shrimp culture.