Bioremediation of inorganic mercury through volatilization and biosorption by transgenic Bacillus cereus BW-03(pPW-05)

• Mercury volatilizing and mercury bioaccumulation was studied in Bacillus cereus BW-03(pPW-05).
• Enhanced bioremediation of mercury was observed by mercury volatilization and accumulation.
• Expression pattern of merA gene and enhancement of mercury removal potential by encapsulation was carried out.
• Pathogenicity test revealed the non-pathogenic nature of the transgenic bacterium.
• This study confirms the application of transformed strain in bioremediation of inorganic mercury.

A transgenic bacterium Bacillus cereus BW-03(pPW-05) was constructed by transforming a plasmid harbouring mer operon of a marine bacterium Bacillus thuringiensis PW-05 into another mercury resistant marine bacterium B. cereus BW-03 with mercury biosorption capability. The transformant was able to remove >99% of mercury supplement in-vitro by simultaneous volatilization (>53%) and biosorption (∼40%). Encapsulation of the transformant increased its mercury removal potential to almost 100%. Additionally, B. cereus BW-03(pPW-05) could resist wide variations of salinity (5–30 ppt), pH (Brierley et al., 1989; Chung et al., 1989; Chen and Wilson, 1997; Chakraborty and Das, 2014) and mercury (5–50 ppm) and survived in mercury contaminated simulated environment up to 7 days. –SH and –COOH groups were possibly involved for mercury biosorption under laboratory conditions. The potential for application of this transgenic bacterium for in-situ bioremediation was demonstrated in a microcosm experiment, where it removed 96.4% inorganic mercury synergistically with the normal microbiota.

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