Contaminated soil pollution solution: herbicide eating bugs

Cancer-causing soil pollution from herbicide residues may be avoided in future thanks to researchers from Exeter University, who have identified bacteria which can break down a widely used toxic chemical, scientists will announce tomorrow (Thursday, 09 September 2004) at the Society for General Microbiology’s 155th Meeting at Trinity College Dublin.
Herbicide residues leaking into water sources, or remaining in agricultural soil and landfills, pose a serious threat of cancer to adults and can cause malformation of unborn babies. In the USA and most of Europe a herbicide called mecoprop, which is used to kill broad leaved weeds in cereal crops, has already been found in drinking water at higher than legal limits.

“Mecoprop is so toxic that it is very difficult for the bacteria in our environment to break it down,” says Dalia Zakaria of Exeter University. “After many unsuccessful attempts we eventually found a strain of Burkholderia bacteria that can degrade it, and using molecular studies we detected some genes which allow them to use it as a food material.”

Once bacteria that can break down the herbicide are identified, the scientists hope to grow colonies and seed them into polluted sites to help clear up the dangerous residues. “Even with this tremendously resilient strain, very few of them could degrade mecoprop on their own, they can only successfully break down the herbicide when they act as a community,” says Dalia Zakaria. “We found a strain which completely cleared soil of residues within a week, compared with natural soil bacteria which only managed to break down half the residue.”

“We are also investigating the spontaneous transfer of the genetic material that allows these Burkholderia bacteria to degrade mecoprop between different soil bacteria, which may let us to develop an even more effective strain,” says Dalia Zakaria.

By introducing mecoprop-degrading bacteria into contaminated sites, and improving conditions for the bacteria to encourage their best performance, the scientists hope they will soon be able to clean the environment.

Understanding the way the bacteria operate will also allow the scientists to provide advice to farmers and landfill operators to avoid creating the conditions which slow down spontaneous mecoprop breakdown.