THE GROWTH PROCESS AND THE MINERALOGY OF MANGANESE OXIDES BY MOCROBIAL MEDIATION

Many slide glasses were set up in the well seawater supply system for aquaria at the Marine Science Museum of Tokai University，where manganese oxides are precipitating by microbial mediation。Manganese-oxidizing bacteria and oxides on the slide glasses were examined in time-series and the growth process of manganese oxides was observed.At first，bacteria attached to the slide glass scatteringly and then got together.The clumped bacteria were decomposed by bacteriolysis.With bacteriolysis，manganese oxides started to precipitate.Manganese oxides grew from doughnut-shaped holdfasts to cauliflower-shaped ones through dome-shaped ones。The honeycomb structure characteristic to marine manganates appeared on the doughnut-shaped holdfasts.Manganese oxide minerals formed by microbial mediation in seawater(Mn I D12锡D1：ca.50ppm；pH：ca.8.0)were investigated by combinations of various manganese-oxidizing bacteria and seawater.The minerals produced were hydrohausmannite，feitknechtite(β-MnOOH)，manganite(γ-MnOOH)，10A-D4°(Buserite Or Todorokite)and unnamed MnO(JCPDS Card：42-1316)，although manganese oxides were not precipitated in some bacterium-seawater combinations.Each oxide mineral was formed by direct oxidation of Mn I D12 ii D1 without intermediates.High valence oxides were formed when the manganese-oxidizing activity of bacteria was high，and vice versa。Mn(IV)oxide minerals in marine environments may be formed by microbial catalysis rather than by pure inorganic processes.

Many slide glasses were set up in the well seawater supply system for aquaria at the Marine Science Museum of Tokai University, where manganese oxides are precipitating by microbial mediation. Manganese- oxidizing bacteria and oxides on the slide glasses were examined in time-series and the growth process of manganese oxides was observed. At first, bacteria attached to the slide glass scatteringly and then got together. The clumped bacteria were decomposed by bacteriolysis. With bacteriolysis, manganese oxides started to precipitate. Manganese oxides grew from doughnut-shaped holdfasts to cauliflower-shaped ones through dome-shaped ones. The honeycomb structure characteristic to marine manganates appeared on the doughnut-shaped holdfasts.Manganese oxide minerals formed by microbial mediation in seawater (MnィイD12+ィエD1:ca.50 ppm; pH: ca.8.0) were investigated by combinations of various manganese-oxidizing bacteria and seawater. The minerals produced were hydrohausmannite, feitknechtite (β-MnOOH), manganite (γ-MnOOH), 10 AィイD4゜ィエD4 manganate (buserite or todorokite) and unnamed MnOィイD22ィエD2 mineral (JCPDS Card: 42-1316), although manganese oxides were not precipitated in some bacterium-seawater combinations. Each oxide mineral was formed by direct oxidation of MnィイD12+ィエD1 without intermediates. High valence oxides were formed when the manganese-oxidizing activity of bacteria was high, and vice versa. Mn(IV) oxide minerals in marine environments may be formed by microbial catalysis rather than by pure inorganic processes.