Isolation and characterization of heterotrophic nitrification–aerobic denitrification and sulphur-oxidizing bacterium Paracoccus saliphilus strain SPUM from coastal shrimp ponds

Abstract

The Paracoccus sp. is one of the best-characterized prokaryote that has served as a model organism to study the dentrification and sulphur oxidation processes. However, its ability of dentrification and sulphur oxidation in coastal shrimp ponds is not reported much. In the present work, the Gram-negative, neutrophilic, facultatively lithoautotrophic bacterium Paracoccus saliphilus strain SPUM isolated from coastal shrimp ponds of Urran, Maharashtra, was studied for its efficiency of simultaneous heterotrophic nitrification–aerobic denitrification and sulphur oxidation processes. The maximum removal rate of nitrite and nitrate was 11.22 ± 0.31 and 14.17 ± 0.31 mg of NO3-N/l respectively after 24 h of incubation, while the sulphatesulphur production observed was 190 ± 4.3 mg l−1 with a change in pH from 8.0 to 7.4 ± 0.08 after 12 days of incubation. The strain was characterized using universal 16S rRNA gene primers revealing high similarity (> 99%) with Paracoccus saliphilus belonging to α- proteobacteria. The isolate could express sulphate thiolesterase/sulphate thiohydrolase, soxB gene which is essential for sulphur oxidation. From all the results, it has been found that the strain SPUM could play a major role in simultaneous aerobic nitrification/denitrification and sulphur oxidation processes to overcome the toxicity of nitrogenous and sulphur-reducing compounds respectively in coastal aquaculture and wastewater systems.