Manganese transformations by marine Bacillus species,

ABSTRACT. A wide variety of micro-organisms promote the oxidation or reduction of manganese, through indirect or direct mechanisms. An example of the latter category is Bacillus SGl, a marine organism isolatefJrom a aear-shore manganese sediment. Its mature domwnt spores catalyze the oxidation ofMn to Mn +. The process requires molecular oxygen and is catalyzed by a spore coat component. The manganese oxide (Mn02) produced remains bound to the The vegetative cells do not have the oxidizing capacity. They are able to reduce Mn + to Mn + under low-oxygen conditions. The reducing activity has a pH optimum of 7.5 and is abolished by preheating of the cells at 90° C for 5 minutes. Addition of mercuric chloride (HgC12) (final concentration 0.01%) to cells which are actively reducing manganese oxide causes immediate cessation of the process. Manganese oxide reduction is also inhibited at high oxygen tensions and by inhibitors of the electron transport system. Bacillus cells contain b- and c-type cytochromes which are oxidized in situ when manganese oxide is added to an anoxic cell suspension. The results suggest that vegetative cells may use the manganese oxide formed by the spores from which they germinate as a terminal electron acceptor. The possible applications of manganese transforming micro-organisms in human society are discussed

Microbial Communities Inhabiting a Rare Earth Element Enriched Birnessite-Type Manganese Deposit in the Ytterby Mine, Sweden

The dominant initial phase formed during microbially mediated manganese oxidation is a poorly crystalline birnessite-type phyllomanganate. The occurrence of manganese deposits containing this mineral is of interest for increased understanding of microbial involvement in the manganese cycle. A culture independent molecular approach is used as a first step to investigate the role of microorganisms in forming rare earth element enriched birnessite-type manganese oxides, associated with water bearing rock fractures in a tunnel of the Ytterby mine, Sweden. 16S rRNA gene results show that the chemotrophic bacterial communities are diverse and include a high percentage of uncultured unclassified bacteria while archaeal diversity is low with Thaumarchaeota almost exclusively dominating the population. Ytterby clones are frequently most similar to clones isolated from subsurface environments, low temperature milieus and/or settings rich in metals. Overall, bacteria are dominant compared to archaea. Both bacterial and archaeal abundances are up to four orders of magnitude higher in manganese samples than in fracture water. Potential players in the manganese cycling are mainly found within the ferromanganese genera Hyphomicrobium and Pedomicrobium, and a group of Bacteroidetes sequences that cluster within an uncultured novel genus most closely related to the Terrimonas. This study strongly suggest that the production of the YBS deposit is microbially mediated