Infrared Beamline Reveals Toxin-Reducing Microbes

Lawrence Berkeley Lab scientists have discovered a bacteria that thrives on toxic waste. A Fourier-transform infrared (FTIR) spectromicroscopy beamline (Beamline 1.4.3) was implemented to identify the toxin-devouring microbes. The bacteria detected converts hexavalent chromium (Cr 6+) a widespread industrial contaminant, into a safer, stable compound (Cr 3+). " Basically, the bugs eat the waste, " said Paul Preuss, a spokesperson for Lawrence Berkeley Lab.Cevera, made the discovery by examining core samples from 75 meters beneath a toxic waste containment site in Idaho. By using infrared spectromicroscopy, they were able to follow the reduction of toxic material among populations of living organisms on minerals: Lawrence Berkeley reports this is die first time that biogeochemical transformation of Cr 6+ on a mineral surface has been nondestructively monitored and studied. Since infrared light does not kill bacteria, the transformation of Cr 6+ could be monitored as it occurred. Distinct infrared absorption bands served dual functions-as chemical markers to detect different chromium species, and as biological markers to detect the presence and activity of microorganisms on specimen surfaces. The brightness of the infrared radiation from the beam-line also made spatially resolved spectromicro-scopy possible. Previously, two mechanisms for reducing Cr 6+ compounds were postulated. The biological mechanism requires the presence of microorganisms to aerobically reduce the Cr 6+. The chemical mechanism relies on metal oxides, such as Fe(II) compounds, to catalyze the Cr 6+ reduction reaction. Working with an infrared beamline over a five-day period, the researchers applied Fourier transform spectromicroscopy to observe the steps in the reduction process and the precise location of the reduced chromium. In addition, the effects on the biotic reduction process of common organic co-contaminants, such as toluene vapor, were evaluated. " The infrared is the end of the spectrum not usually associated with synchrotrons, " said Holman, " but for us it's perfect-and not only because it's non-destructive of organisms. You have an extremely complicated spectrum in the 10 µm region [the dimension of the beam]. We identified markers in this spectral region that tracked the key compounds that undergo changes. We could resolve the spectrum in time, to follow the different steps of the reduction , and also in space, to see exactly where the reactions were happening. " On the magnetite samples with no living bacteria, no significant changes were evident. On samples with living microorganisms (Arthrobacter oxydans) in the absence of toluene, a weak chromium reduction …