te l C

inferred to be present, as deduced from Jahn–Teller distortion of the local structure. The physical geometry and structural details of the coatings suggest formation within microbial biofilms. The biogenic Mn oxides are stable with respect to trans-2005b,c). Mn oxides are among the strongest of naturally ubiquity of Mn(II)-oxidizing microorganisms in the envi-ronment (Tebo et al., 2004) and upon the much faster rates of Mn(II) oxidation at circum-neutral pH when catalyzed by microorganisms as compared to rates of homogeneous or surface-mediated abiotic mechanisms (Morgan, 2005)