Methylmercury degradation by Pseudomonas putida V1

• The removal of mercury by P. putida V1 was influenced by the type of mercury.
• The merA gene was highly similar (100%) to the mercuric reductase gene of other Pseudomonas spp.
• The merB gene could be not detected in P. putida V1.
• Tests using radioactive 14C-methylmercury indicated an uncommon release of 14CO2.
• Strain V1 did not present the normal pattern of degradation by a broad- spectrum mer operon.

Environmental contamination of mercury (Hg) has caused public health concerns with focuses on the neurotoxic substance methylmercury, due to its bioaccumulation and biomagnification in food chains. The goals of the present study were to examine: (i) the transformation of methylmercury, thimerosal, phenylmercuric acetate and mercuric chloride by cultures of Pseudomonas putida V1, (ii) the presence of the genes merA and merB in P. putida V1, and (iii) the degradation pathways of methylmercury by P. putida V1. Strain V1 cultures readily degraded methylmercury, thimerosal, phenylmercury acetate, and reduced mercuric chloride into gaseous Hg(0). However, the Hg transformation in LB broth by P. putida V1 was influenced by the type of Hg compounds. The merA gene was detected in P. putida V1, on the other hand, the merB gene was not detected. The sequencing of this gene, showed high similarity (100%) to the mercuric reductase gene of other Pseudomonas spp. Furthermore, tests using radioactive 14C-methylmercury indicated an uncommon release of 14CO2 concomitant with the production of Hg0. The results of the present work suggest that P. putida V1 has the potential to remove methylmercury from contaminated sites. More studies are warranted to determine the mechanism of removal of methylmercury by P. putida V1.