Geomicrobial Exploration of Sulfur Oxidizing Bacteria Indigenous to Kapurdi and Jalipa Lignite Mine Site, Rajasthan

The metabolic versatility and potential of microbes enables their survival and growth in harsh condition such as sites ravaged by mining activities. The Kapurdi lignite deposit of the Barmer Basin is one of the important Tertiary lignite deposits underlying the Great Indian Thar desert in the north-western part of Rajasthan. The diversity of culturable sulfur oxidizing bacteria (SOB) in Kapurdi and Jalipa lignite mine site, Barmer, Rajasthan was assessed in this study. Bacteria were isolated by plating on selective thiosulfate mineral media, and dominant isolates were identified from their physiological characteristics and 16S rRNA gene sequences. The obligate chemolithotrophic SOB were identified as Thermithiobacillus sp. strain KO11, KO12, KO13 (OP788122, OP788123, OP788124). Whereas heterotrophic SOB was identified as Bacillus sp.strain KO1 (OP788112), Bacillus sp. strain KO2 (OP788113), Bacillus sp.strain KO3 (OP788114), Enterobacter sp.strain KO4, KO5, KO6, KO9 (OP788115, OP788116, OP788117, OP788120), Leclercia sp. Strain KO7(OP788118), Pantoea sp. strain KO8(OP788119), and Rhodococcussp.strain KO10 (OP788121). The culture condition was optimized for the two most potential SOB i.e., Thermithiobacillus sp. strain KO11 and Leclercia sp. strain KO7. Both the isolates grew well and produced maximum amount of sulfate in thiosulfate mineral media at pH 8.0 and with 40 mM of thiosulfate substrate. Thermithiobacillus sp. strain KO11 had the optimum growth at 45°C indicating its thermophillic nature whereas, Leclercia sp. strain KO7 had optimum growth at 35°C. This study significantly enhances our knowledge of native bacteria in mining impacted environments and their role in biogeochemical cycling of sulfur.