광물학/광상학/지체구조학 10월30일(토)
Metal Reduction and Iron Biomineralization by A Psychrotolerant Fe(III)-Reducing Bacterium, Shewanella waksmanii , Isolated From Microbial
Mat at Naha Hydrothermal Vent, Loihi Seamount, Hawaii
Since so much of our planet is generally cold, i.e. below 4°C, it is not surprising that psychrophiles, which live in cold conditions, are very common amongst a wide variety of habitats. Although microbial reduction of Fe(III) plays an important role in iron and carbon biogeochemistry and contributes to magnetization of the sediments in subsurface environments, the psychrotolerant (< 10°C) microbial metal reduction and biomineralization are only beginning to be studied. To learn more about the physiological properties of Fe(III)-reducing microorganisms growing at low temperatures, we isolated a psychtrotolerant, dissimilatory Fe(III)-reducing bacterium from microbial mat at hydrothermal vent. A Shewanella specie, closely related to Shewanella waksmanii, isolated from cold marine environments reduced Fe(III)-species and other metals such as Co(III), Cr(VI) and Mn(IV) as well as formed magnetite and siderite at temperature ranging from 0 to 37°C. Unlike mostly superparamagnetic magnetite (< 35 nm) produced by mesophilic (20-35°C), dissimilatory Fe(III)-reducing bacteria, the psychrotolerant bacteria produced mainly well-formed single-domain magnetite (>35 nm) at temperature ranges from 14 to 37°C. The Fe(III) reducing bacterium facilitated siderite formation under a CO
2atmosphere and in HCO
3-buffered medium. These results indicate that microbial Fe(III) reduction may play important roles in iron and carbon biogeochemistry as well as sediment magnetism in cold natural environments over geological times. The biomineralization processes involving Fe(III)- reducing bacteria may also provide an CO
2fixation in cold oceanic environment.
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