UV Raman spectroscopic data measured at two distinct conditions, low and high laser power, establish that the manganese oxide (SP6-MnQ(x)) produced by the freshwater bacterium (Leptothrix discophora SP-6) closely resembles the 3 x 3-tunnel todorokite among the MnO2 materials studied. Under the two conditions, the effect of hydration/cation and the phase transition of todorokite or SP6-MnO., to Mn3O4 or birnessite will be described. A higher concentration of Mg2+ incorporated in the framework of the SP6-MnO, than in todorokite is probably responsible for the formation of a new Raman band obtained at high laser powers, matching the most intense UV Raman band of synthetic birnessite. Also, we present the assignment of Raman bands for todorokite mineral and discuss the mutual exclusion principle that should hold for all the MnO2 materials studied. These experiments provide characterization of hydrous, poorly crystalline, or nanocrystalline metal oxides, which are frequently difficult to identify.