Updated FTP location. 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.