Cycling of Biogenic Mn-Oxides in a Model Microbial Predator-Prey System

2006 
The phase distribution and bioavailability of both essential and toxic trace metals can be profoundly impacted by trophic transfer in microbial food webs. A model microbial predator-prey system was used to elucidate the possible transformations of biogenic manganese oxides as they were consumed by protozoan predators along with their bacterial prey. The ciliated protozoan Tetrahymena thermophila and the Mn-oxidizing bacterium Leptothrix discophora SS-1 were chosen as predator and prey species, respectively. The following processes were evaluated: adsorption and pinocytosis of Mn(II), regeneration and bioaccumulation of biogenic Mn-oxides, and excretion of Mn associated with waste matter. Changes in Mn oxidation state and phase distribution were assessed by observation of dissolved Mn(II) concentrations coupled with a comparison of Mn-oxide and total Mn concentration over time. Mn(II) adsorption to and pinocytosis by T. thermophila were not significant at Mn levels up to 100 μM. At the experimental pH of 7...
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