Project description:In order to gain insight into how bacteria respond to manganese (II) and relate to oxidation, the shotgun proteomics approach was applied to a potential Mn (II) oxidizing Serratia marcescens strain cultivated in the absence and presence of Mn (II). The LG1 strain, which grew equally well in these two conditions, presented a set of proteins related to the cellular processes vital to its survival and proteins that ensured its good adaptation and tolerance to Mn (II). The multicopper oxidase CueO was identified, indicating its probable participation in the Mn (II) bio-oxidation, but its expression was not modulated by the presence of Mn (II).Through these findings, we reiterate the ability of LG1 to be applied successfully in the bioremediation of Mn (II) environments and the efficiency of the shotgun approach in obtaining the first total shotgun proteome of this specie.
Project description:Fe(II) can be oxidized by mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria to Fe(III), leading to mineral precipitation. However, the effects of this process on the metabolism and reproduction ability of the Fe(II)-oxidizing bacterial cells have not yet been quantified. In this study, we investigated the effects of Fe(II) on the mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria Acidovorax sp. BoFeN1 by performing cell plate counts, chemical analyses, and scanning electron microscopy (SEM) imaging. The result showed that nitrate-reducing Fe(II)-oxidizing bacteria Acidovorax sp. BoFeN1 undergoes a striking physiological state in which respiration persists while cell reproduction collapses after their oxidation of Fe(II). Across 0.1–10 mM Fe(II), colony-forming units dropped by up to 103-fold, yet acetate consumption remained largely unaffected and nitrate reduction was even slightly promoted. SEM-EDS reveals extensive Fe(III) encrustation on cells. Adding an Fe(III) chelator, citrate, restored reproductive capacity without notably changes in Fe(II) oxidation or nitrate reduction, indicating that it was the products of Fe(II) oxidation, the secondary Fe(III) minerals, that impaired cell reproduction. These findings uncover a mineral encrustation-driven uncoupling between respiration and reproduction, suggest how natural organic ligands may buffer NRFeOx bacterial communities in Fe-rich anoxic environments, and point to cellular-level levers for mitigating denitrification failures and N2O risks in engineered and natural systems.