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IN ADDITION TO these and other active roles that microbes play in geochemical processes, the simple presence of bacteria can have indirect geochemical consequences. Liane G. Benning, a geochemist at the University of Leeds, in England, is studying how microbes contribute to the formation of porous silica crusts. She told symposium attendees about her lab's successful use of synchrotron-based infrared microspectroscopy to follow the course of silica biomineralization in vitro. Her results show that cyanobacteria provide a surface for silica accumulation by inorganic precipitation--but that they don't actively contribute to silica formation. Benning's work, as well as that of the other symposium speakers, demonstrates that the chemistry that occurs close to microbial surfaces is very different from that of the bulk solution, Cooper pointed out. "The chemistry of this 'microbial space' becomes even more complex when the microorganism is in contact with a mineral surface. The science of biogeochemistry is attempting to uncover the processes that occur at these interfaces and explain how they affect larger environmental cycles," he added. High-resolution synchrotron-based methods such as scanning transmission X-ray microspectroscopy and X-ray absorption fluorescence microscopy are helping to fuel discoveries in this area. This emerging area of geochemistry is brimming with opportunity, Warren believes. She pointed out that because microbes are widely distributed on Earth--microorganisms have been found in even the harshest of environments, including deep-sea hydrothermal vents, toxic abandoned mine sites, and even deep under Earth's surface--their influence is likely to be profound. "We are only just beginning to scratch the surface of microbes' role in geochemistry." |
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