Isolation and Characterization of Heterotrophic Sulphur Oxidizing Bacteria From Different Ecological Niches

Most of the sulphur in soil environment (>95% of total sulphur) is bound to organic molecules and is therefore not directly plant-available. The transfer of sulphur between the inorganic and organic pool is entirely caused by the activity of the soil biota, particularly the soil microbial biomass. Thus attempts are made to isolate a best sulphur oxidizing bacteria from different ecological niches. A total of nine heterotrophic Sulphur Oxidizing Bacterial (SOB) isolates were obtained from four different sources viz., sewage water (Coimbatore), biogas slurry (Coimbatore), alkaline soil (Trichy) and groundnut rhizosphere soil (Aliyar Nagar) using enrichment technique in Modified thiosulphate broth. All the isolates were found to be Gram positive short rods and they were able to reduce the pH from 8.0 and utilize thiosulphate as sulphur source and glucose as carbon source. The colonies were smooth, round, straw yellow colored. Based on pH reduction and sulphate production, the SOB isolate BGS 2 was screened as the best isolate. The isolate BGS2 reduced the pH upto 3.5 from an initial 8.0 mg sulphate per 100 mL and produced 79.2 mg sulphate per 100 mL of growth medium