Redox reaction associated with microbial elemental respiration is a ubiquitous process in sediments as well as suspended particles in water, regardless of temperature or pH/Eh conditions. Particularly, changes in elemental redox states (both structural form in the mineral or dissolved elemental form in the water) induced by microbial respiration result in the unexpected biogeochemical reactions in the light of biotic/abiotic mineralization. The objective of the present study is to investigate the microbe-mineral interaction in the acido-hyperhtermal Norris Geyser Basin in Yellowstone National Park, USA to understand the mechanism of biogeochemical process in extreme environment. The present study focused on distinguishing biotic and abiotic process during the secondary phase mineral formation in extreme environment particularly Fe and As redox cycle utilizing x-ray diffraction, scanning electron microscope with energy dispersive x-ray spectroscopy, and X-ray absorption near edge structure, as well as water system analysis including inductively coupled plasma (ICP)-atomic emission spectrometer and liquid chromatography with ICP-mass spectroscopy with filtrated supernatant. The clay slurry collected from the active hot-spring of the NGB area (pH=3.5 and Temperature=78 degree C) was incubated with or without the growth medium (Natural and Enrichment set). The control was prepared in the same condition except adding the glutaraldehyde to eliminate the microbial activity. The secondary phase mineral formation with elemental compositions of the oxidative phase of Fe and As, and K was identified as ‘Pharmacosiderite’ only in enrichment set suggesting a major role of extremophiles are closely linked with the mineral formation. The considerable population of Fe-oxidizer (Metallosphera yellowstonensis MK-1) and As-oxidizer (Sulfurihydrogenibium sp.) was detected by phylogenetic analysis in the present study area supporting the major role of extremophiles in biotic mineral alteration/formation process. Furthermore the As-redox reaction was observed only in the enrichment set, while previous studies reported the inhibition of As-oxidation in the low pH conditions that may indicate the microbial oxidation of As in the present study is critical factor for the mineral formation in the extreme environment such as NGB area, Yellowstone National Park. The possible biotic/abiotic mechanism or process in mineral alteration/formation in extreme environment will be discussed.

Microbially induced redox reaction of Fe/As in extreme environment, Norris Geyser Basin, Yellowstone National Park, USA

251st National Meeting (2016)

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