Identification of metallothionein gene in Staphylococcus warneri strain G isolated from industrial effluent in Sri Lanka

Abstract

Controlling pollutants has become a crucial requirement with the world’s population increase and urbanization. Studies on bacteria with metal tolerance capabilities have revealed the presence of heavy metal tolerant mechanisms and their potential use in bioremediation. Identification and isolation of genes that confer metal resistance in bacterial isolates is important as they can be used to modify organisms using genetic engineering to enhance bioremediation abilities. Metallothionein is an intracellular protein found in both prokaryotes and eukaryotes that has the ability to bind heavy metals via thiolate bonds and thereby reduce the toxic effects of heavy metal ions to living organisms. Heavy metal tolerance analysis showed that Staphylococcus warneri strain G, which has been previously isolated from a textile dyeing industry has metal tolerance ability in the order of Pb2+ (1000 ppm) > Cd2+ (100ppm) > Cu2+ (25ppm). Although metallothionein gene is known to present in S. epidermidis genome, it has not yet been assigned in any of the S. warneri genomes. Primers were designed exploiting the S. epidermidis gene sequences to amplify a region of 295 bp flanking the complete metallothionein gene and to amplify a region of 628 bp which included the complete sequence of the possible regulator gene along with the complete metallothionein gene of Staphylococcus spp. Both Polymerase Chain Reaction amplifications resulted bands of expected sizes for S. warneri strain G where the nucleotide sequencing of the two amplicons showed a similarity of 98% for the complete metallothionein gene and for the complete regulator gene present in S. epidermidis 949_S8. It was concluded from the above study that S.warneri strain G has the potential to synthesize metallothionein which can contribute in the heavy metal tolerance of S.warneri strain G.