Characterization of mercury protein targets in Geobacter sulfurreducens PCA

Fe-reducing bacteria (FRB) play a pivotal role in regulating the biogeochemical cycling of mercury (Hg) and its associated ecological risks, while a systematic understanding of the molecular targets affected by Hg stress in these bacteria remain limited. In this study, we employed gel electrophoresis coupled with inductively coupled plasma mass spectrometry (GE-ICP-MS) to investigate the protein interaction responses to Hg stress in the model FRB Geobacter sulfurreducens PCA. This approach allowed us to identify Hg-binding proteins and characterize their functional implications. For the first time, we successfully resolved metalloproteins in this strain using GE-ICP-MS and identified 13 specific Hg-binding proteins, revealing critical molecular targets beyond previously known pathways. Functional analysis indicated that Hg binding to key enzymes in central carbon metabolism (gapA, eno, and gltA) and the ATP synthase subunit (atpD) induced a cellular energy deficit. Concurrently, Hg impaired protein folding (groES and degP) and synthesis machinery (tuf1 and rplI), thereby disrupting the production and function of essential proteins. These processes initiate a self-limiting cascade that ultimately suppresses the Hg methylation by disrupting its essential prerequisites, which provides a mechanistic explanation for the observed fluctuation of methylation ability. These findings demonstrate the utility of GE-ICP-MS in microbial metallomics, offering​ new molecular insights into the mechanisms of microbial Hg adaptation.