Role of a two-component sensing system and a metal efflux system in bacteria methylating Hg and demethylating MeHg

Methylmercury (MeHg) is a strong neurotoxin and is mainly produced by sulfate-reducing bacteria (SRB) in the environment. However, the mechanisms of Hg methylation and MeHg demethylation are still poorly understood. We study the model SRB strain Pseudodesulfovibrio hydrargyri BerOc1 and we have generated BerOc1 mutants impaired with a metal efflux system and with a two-component sensing system involved in Hg regulation, and probably Hg sequestration. These mutants showed specific phenotypes in Hg methylation and MeHg demethylation. Our objective is to identify and quantify the various Hg species in the wildtype and mutants upon Hg methylation and MeHg demethylation. For that, we will use Hg L3-edge High-Energy Resolution Fluorescence Detected -X-ray Absorption Near Edge Structure spectroscopy (HERFD-XANES) from FAME-UHD beamline that proved powerful to determine Hg species at relevant environmental levels