In this study two new species of the genus Sulfurimonas, namely S. marisnigri and S. baltica are described, originating from the Black Sea and the Baltic Sea, respectively. The results of this thesis showed the existence of a bacterial metabolism connecting the marine Mn and S cycles with implications on the water column biogeochemistry of euxinic basins. Further, the precipitation of Mn(Ca)CO3 in pure culture experiments might offer a plausible explanation for sediment layers rich in Ca-rich manganese carbonate, which is discussed and hypothesized.