German researchers have found bacteria that happily eat the pungent solvents at the heart of everything from typewriter correction fluid to paint -- chlorinated benzene chemicals. These microbes should help engineers to design better ways of treating water and soil polluted with the toxic compounds.
Chlorobenzenes hang around in the environment for a long time and can accumulate in the food chain. Already, different types of bacteria acting together in 'bioreactors' can break down chlorobenzenes.
From such a bioreactor, Lorenz Adrian of Technische Universität, Berlin, and his colleagues have now isolated and identified the first individual bacterial strain that can degrade chlorobenzenes on its own. In fact, it seems that the bugs -- called CBDB1 -- cannot live without the noxious solvent.
"When we know what type of bacteria are involved in the process we can change the environmental conditions to suit them. This will speed up the process and allow more pollution to be treated," says Werner Hegemann, a civil engineer also at Berlin's Technische Universität. Hegemann has been studying the removal of chlorobenzene in bioreactors for over ten years, and CBDB1 was isolated from one of his systems.
Adrian's team has already discovered that CBDB1 needs a hydrogen source to complete its energy-producing loop. Adding extra hydrogen might help the bacteria to grow, cleaning up more pollution. Similarly, the team can now look for chemicals that may be blocking chlorobenzene degradation and try to remove them.
Biological clean-up methods can be cheaper than conventional chemical and physical pollution treatments. And they have a crucial advantage: "In conventional treatments, the pollution is merely concentrated or moved," Hegemann says. "With biological treatment the pollution is degraded, ultimately to carbon dioxide. The contaminants really disappear."
CBDB1 uses chlorobenzene in its respiration in the same way that we use oxygen: as a receptor for electrons. For most organisms, these electrons come from the carbon-based compounds that they eat. But CBDB1 takes them from hydrogen; oxygen poisons them, the team reports in