Mercury resistance in Sporosarcina sp. G3

Mercuric reductase (MerA) enzyme plays an important role in biogeochemical cycling and detoxification of Hg and recently, has also been shown to be useful in clean up of Hg-contaminated effluents. Present study describes isolation of a heavy metal-resistant isolate of Sporosarcina, which could tolerate up to 40, 525, 210, 2900 and 370 μM of Cd, Co, Zn, Cr and Hg respectively. It was found to reduce and detoxify redox-active metals like Cr and Hg. The chromate reductase and MerA activities in the crude cell extract of the culture were 1.5 and 0.044 units/mg protein respectively. The study also describes designing of a new set of highly degenerate primers based on a dataset of 23 Firmicute merA genes. As the primers encompass the known diversity of merA genes within the phylum Firmicutes, they can be very useful for functional diversity analysis. They were successfully used to amplify a 787 bp merA fragment from the current isolate. A 1174 bp merA fragment was further cloned by designing an additional downstream primer. It was found to show 92% similarity to the putative merA gene from Bacillus cereus AH820. To the best of our knowledge, this is the first report of mercury resistance and merA gene sequence from Sporosarcina.