Calcite Precipitation by Rhodococcus sp. Isolated from Kotumsar Cave, Chhattisgarh, India

The precipitation of carbonate minerals by Rhodococcus sp. strain S14 isolated from Kotumsar cave, Chhattisgarh, India is reported. The speleothems at Kotumsar showed high microbial cell enumeration on B4 agar; iron agar (3.4 x 10⁵ CFU/g) and sulphite agar (7.2 x 10² CFU/g). National Centre for Biotechnology Information database was used for the BLASTn sequence search of 16S rRNA sequences. The S14 strain gave similarity scores of ≥99% with the respective organisms on the database. The strain was identified as Rhodococcus sp. Culture experiments performed using the isolated strains suggested that the rate of precipitation was dependent on pH, temperature and bacterial growth. Rhodococcus sp. S14 strain induced the formation of calcite in vitro and the biominerals produced were calcified spherulites with pores (as imaged with SEM). The precipitate, at the end of the experimental period of 35 days, had the appearance of coccoliths. This is the initial report on the possible involvement of Rhodococcus sp. in the precipitation of carbonates at Kotumsar cave.