HR: 09:45h
AN: B11B-07    [Abstracts]
TI: Coupled Mn(II) Oxidation Pathways by a Planktonic Roseobacter-like Bacterium
AU: * Hansel, C M
EM: hansel@stanford.edu
AF: Stanford University, Dept. of Geological and Environmental Sciences Bldg 320 - Rm 118, Stanford, CA 94305-2115 United States
AU: Francis, C A
EM: caf@stanford.edu
AF: Stanford University, Dept. of Geological and Environmental Sciences Bldg 320 - Rm 118, Stanford, CA 94305-2115 United States
AB: Bacteria belonging to the Roseobacter clade of the alpha-Proteobacteria are numerically abundant in coastal waters, ecologically significant in the cycling of (in)organic sulfur, and occupy a wide range of environmental niches. Here we reveal that Roseobacter-like bacteria may play a previously unrecognized role in the oxidation and cycling of manganese (Mn) in coastal waters. A diverse array of Mn(II)-oxidizing Roseobacter-like species were isolated from Elkhorn Slough, a coastal estuary adjacent to Monterey Bay, California. One isolate (designated AzwK-3b), in particular, rapidly oxidizes Mn(II) to insoluble Mn(III, IV) oxides. Interestingly, AzwK-3b is 100% identical (at the 16S rRNA level) to a previously reported Pfiesteria-associated Roseobacter-like bacterium, which does not posses the ability to oxidize Mn(II). Manganese(II) oxidation rates by live cultures and cell-free filtrates are substantially higher when incubated in the presence of light. Rates of oxidation by washed cell extracts, however, are light independent, which are actually identical to rates by cell-free filtrates incubated in the dark. Thus, AwwK-3b induces two Mn(II) oxidation mechanisms when incubated in the presence of light as opposed to predominantly direct enzymatic oxidation in the dark. Within the light, production of photochemically-active metabolites is coupled with initial direct enzymatic Mn(II) oxidation, resulting in substantially accelerated Mn(II) oxidation rates. Thus, Roseobacter-like bacteria may not only greatly influence Mn(II) oxidation and cycling within coastal surface waters, but may also induce a novel photo-oxidation pathway providing an alternative means of Mn(II) oxidation within the photic zone.
DE: 0448 Geomicrobiology
DE: 0461 Metals
DE: 0463 Microbe/mineral interactions
DE: 0471 Oxidation/reduction reactions (4851)
SC: Biogeosciences [B]
MN: Fall Meeting 2005