8. E. Anne Edwards (2014) Breathing the unbreathable SCIENCE VOL 346

·       Catalina Ignacia Aguilera Flores

 E. Anne Edwards (2014) Breathing the unbreathable SCIENCE VOL 346

As humans, we have a real concern about what is happening in our environment, how we affect it and the most important how can we remedy our actions. There is one group of chemicals called organohalides that can be produced by volcanic emissions, lighting strikes, plants, animals and microbes as hormones; but there are synthetic organohalides with a huge history of contaminated sites around the world, some of them can be toxic at high concentrations. This are versatile chemicals, highly stable and poorly soluble in water, known for containing at least one carbon atom bound to a halogen atom, such as chlorine, bromine, fluorine or iodine. They include tetrachloroethene (PCE), trichloroethene (TCE), chlorofluorcarbons (CFCs) and compounds like Teflon.

Life as always continues marveling us with certain microbes that are able to break down organohalides pollutants. Clues that anaerobic microbial communities could reduce dehalogenate organohalides emerged 50 years ago with the idea of using them to detoxify the environment. Evidence that showed how microbes could grow using the energy from the carbon-halogen bond made a big boom on the scientific community, using them for industrial applications such as bioremediation. At the center of this application are alluring microbes that use organohalides as terminal electron acceptor in their metabolism, they literally breathe these molecules. In the process, the halogen substitutes are removed from the organic backbone.

These incredible organohalides-respiring microbes are phylogenetically diverse, found around the planet in both freshwater aquifers and marine sediments. For example, Dehalococcoides and Dehalobacter only breathe organohalides. This carries a problem that is still not solved in the scientific community, the huge difficulties for cultivating these microbes in strict anaerobic conditions. Anaerobic environments are found in nature, stablished in sediments and in the subsurface.

Genomes of these exceptional microbes have a giant diversity of genes coding for enzymes that catalyze reductive dehalogenation present in the GenBank, yet, for most of these enzymes the substrates remain unknown. Reductive dehalogenase enzymes require cofactors to help the reaction, including vitaminB12.

Bommer, reported the crystal structure of an enzyme from the bacterium Sulfurospirillum miltivorans that catalyzes the carbon-halogen bond in PCE and TCE. Also the vitamin is in fact buried, and protected in the enzyme. Kwnoledge of the active site of the enzyme will provide new models to structure-based substrates, including some of the most toxic organohalides.

Nature published a complementary paper that describes the structure for a distinct but similar B12-dependant reductive dehalogenases found in aerobic microbes. As team, these brand new structures begin to reveal the relationship between sequence and substrate preferences, helping to anticipate, based on the dehalogenating microbes, the fate of synthetic and natural occurring chemicals.

Is crucial to understand how microbes work with organohalides for the effective management of contaminated sites. Also we must find the best conditions for the microbe to grow and the manipulation of their genomes for a better and deep study. It’s really important in science to complement knowledge with other people, because you never know how much other’s people wisdom can help your theory be more complete.

bien!!