Bacteria play an important role in the breakdown of toxic pesticides: For the first time, researchers have shown that certain types of bacteria are involved in the breakdown of herbicides from agriculture. The microorganisms support the cleaning of the wastewater in special cleaning systems – a vision for more sustainable agriculture?
Herbicides are used specifically in agriculture around the world to prevent weeds from growing on the arable land and ruining the harvest. The chemicals in the pesticides get into the soil and eventually contaminate the groundwater. Some herbicides are considered carcinogenic, so there are legal regulations in Europe for the use of chemicals in the fields. In the United States and Canada, many farms have dedicated purification systems to help reduce groundwater pollution.
Promising cleaning systems
In the USA and Canada, the plant protection product linuron is used to control weeds, which inhibits the photosynthesis of unwanted plants. This organic chlorine compound has been banned in the EU since 2018 because it has a hormone-like effect and is considered carcinogenic and should therefore not get into the groundwater. In America, however, farmers rely on special cleaning methods in order to keep contamination of the water as low as possible. These so-called On-Farm Purification Systems (BPS) filter the wastewater collected during the cleaning of the work equipment before it is discharged into the ground.
The exact functioning of these cleaning systems has not been clarified in detail. It is only known that various bacteria can break down the herbicides in the water. So far these could not be identified. A research team led by Harry Lerner from the Catholic University of Leuven has set itself the task of identifying the responsible bacteria. For their study, the team used the process of isotope-assisted DNA labeling, which enables genetic detection of the various types of bacteria. To get an exact result, they cultivated the bacteria in the BPS systems used in agriculture, which are used to break down linuron.
Identified microbial decomposers of poisons
The investigation revealed that representatives of the bacteria Variovorax, Comamonadaceae and Ramlibacter are involved in the breakdown of the toxic herbicide. The latter were detected for the first time in a BPS matrix – a novelty for research. “Our experiments show that in-situ other microorganisms are responsible for the decomposition of the pollutants than was previously known from laboratory tests,” reports co-author Başak Öztürk from the Leibniz Institute DSMZ – German Collection of Microorganisms and Cell Cultures in Braunschweig.
For the researchers, the result is an important step towards more sustainable agriculture: “The unique thing about our study is that we were able to demonstrate a direct connection between herbicide degradation and the microorganisms responsible for it. I hope that the explanation of how these on-farm purification systems work will also convince German farmers that it makes sense to buy their own small sewage treatment plant, ”says the expert. Their reason: “Establishing the BPS is not cost-intensive and does not require a lot of space. And even if we do not use linuron here in Germany, other herbicides are used that can have a negative impact on the ecosystem. “
Source: Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH; Technical article: Environmental Science & Technology, doi: 10.1021 / acs.est.0c02124