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Biochemistry

An Arsenal to Fight Arsenic

an arsenal

© GMGM

This test allows discrimination between wild type bacterial strains capable of oxidizing arsenic (brown spots) and mutant strains that lost this capacity (yellow spots).


Another bacterial genome sequenced? Yes, but not just any bacterium. Herminiimonas arsenicoxydans  not only lives in arsenic-contaminated waters, it is attracted to arsenic-rich waters. “It's the first type of arsenic-adapted bacteria whose genome and physiology have been fully explained,” says Philippe Bertin from GMGM,1 who headed this project.2

The study published in PLoS Genetics last April3 uncovered how this particular microorganism can oxidize the most poisonous form of arsenic, thus leading to a less mobile and toxic molecule with reduced availability to living organisms in the environment. “It's also the first time that we have observed a series of mechanisms that regulate the adaptive response to arsenic as a whole, providing a very comprehensive view of what goes on.”

Studies are currently underway to find out how H. arsenicoxydans is drawn to milieus that are rich in arsenic. Researchers have already identified which parts of the bacterium might act as a sensor to guide it. Moreover, once in presence of the toxic metalloid, the bacterium absorbs it through an exopolysaccharides matrix, a thick sugar-rich protective layer on its external surface. Another property that makes it a good candidate for environmental detoxification.The team is now cooperating with water treatment companies to implement biological decontamination methods rather than the usual chemical ones. “It's not merely an idea, but something very tangible. Water treatment plans can incorporate the use of these bacteria,” says Bertin.

With tens of millions of people affected by arsenic contamination in their environment, bacteria metabolizing toxic elements represent an attractive tool to restore contaminated sites.

 

Melisande Middleton

 

Notes :

1. Génétique moléculaire, génomique et microbiologie (CNRS / Université Strasbourg 1).
2. Laboratories from several institutions were involved in this research: CNRS, CEA (Saint-Paul-lez-Durance), Génoscope (Evry), Institut Pasteur (Paris), Universités Claude Bernard (Lyon) and Louis Pasteur (Strasbourg).
3. D. Muller et al., “A tale of two oxidation states: bacterial colonization of arsenic-rich environments,” PLoS Genet. 3: 518-530. 2007.

Contacts :

Philippe Bertin
GMGM, Strasbourg.
philippe.bertin@gem.u-strasbg.fr


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