Mutated bacteria are the new pollution busters
Toxic metals and radionuclides are a persistent source of pollution with serious long-term effects on food chains. The good news is that these can be rendered insoluble and therefore immobile by bacteria, a perfect way to reduce toxicity to living systems. Biochemically, the metals and radionuclides are reduced by the microbes to form insoluble and/or immobile forms. In particular, bacteria that use sulphur or iron for reduction are ideal candidates for waste removal as they have an electron transport set up on the envelope or outer coat. One limitation is that any nitrate or oxygen, usually present at waste sites, will inhibit the bioremediation. However, researchers on the EU-funded project ′Bioremediation of toxic metals and radionuclides using naturally evolved bacteria capable of intra-cellular reduction without oxidative stress′ (Bacterometrics) made a breakthrough and found a possible alternative. One way around this problem comes in the form of a ‘safe’ bacterial pathway preventing production of reactive oxygen species that literally poison the cells. The non-toxic proteins from the commonly occurring ChrR enzyme family perform electron transfer processes that strongly reduce oxidative stress and lead to separation of the reduced compounds. Bacterometrics scientists used state-of-the-art spectroscopy, electrochemical titration and size-exclusion chromatography for a structure-function analysis of the wild type and mutant forms of the ChrR enzyme from Escherichia coli. The researchers found that some mutations specifically modify the affinity and possibly docking sites for chromate, while others directly influence the electron transfer mechanism. Evolution has provided the material. Bacterometrics has uncovered new insights into the development of new bioremediation processes for radionuclides and metals.
