Mercury resistance and volatilization by Pseudoxanthomonas sp. SE1 isolated from soil

A mercury resistant bacterial strain SE1 isolated from contaminated soil was identified as Pseudoxanthomonas based on 16s rRNA sequencing. The Hg resistance was examined in both nutrient-rich media as well as low nutrient media and expressed as EC₅₀ and MIC values. Estimated EC₅₀ and MIC values in nutrient-rich media and low nutrient media had the following respective recordings - 22.6 mg L^-1; 23.1 mg L^-1 and 1.4 mg L^-1 and 1.7 mg L^-1. The isolate was able to volatilize inorganic mercury demonstrated by a modified photographic film experiment and subsequently revealed its ability to remove mercury from the solution. The ICP-QQQ-MS analysis of SE1 inoculated solution showed almost 60% of 1.5 mg L^-1 mercury was volatilized in 6 h and almost 40% were accumulated in cell pellets. The mercuric reductase gene <i>mer</i>A was identified in the genome of isolate SE1 and sequenced. The deduced amino acid sequence of <i>mer</i>A gene indicated a sequence homology with different organisms from the alpha proteobacteria group and eukaryotic fungi. <i>mer</i>A encoded enzyme mercuric reductase activity was evident in the crude protein of the isolate. The isolate's ability to resist Hg, it's Hg volatilization potential and the presence of <i>mer</i>A gene and mercuric reductase enzyme demonstrates the potential application of this strain in mercury bioremediation