Consortium of bacteria to clean up soils contaminated with pesticides

Scientists have managed to use what can be described as a “consortium of bacteria” to remove the herbicide atrazine, used to combat a weed that harms sugarcane, from the soil. In addition, they began a series of tests from the combination of bacteria with waste from the industry to see if the sanitation effect is enhanced.

The work is the work of a team that includes Lucas Bazán, from the National University of Tucumán (UNT) in Argentina, as well as Soledad Fuentes and Claudia Benimeli, who work at the Microbiological Industrial Processes Pilot Plant of the National Council for Scientific Research. and Techniques (CONICET) in Argentina.

The goal in this line of research and development is to clean up soils contaminated with different pesticides. To remove contaminating agents, a group of bacteria is used. Trials in recent months focused on decontaminating soils with atrazine, a herbicide widely used in the region to combat plants that harm sugarcane cultivation.

The group has been studying, for more than five years, the action of a group of actinobacteria, versatile and ubiquitous bacteria capable of living in different environments such as water, soil and sediments.

These bacteria can clean up soils contaminated with pesticides, as has been verified in tests carried out in the laboratory. These bacteria are of the genus Streptomyces and have a filamentous appearance.

Claudia Benimeli, Lucas Bazan and Soledad Fuentes. (Photo: National University of Tucumán / Argentina Investiga)

Dr. Fuentes told Argentina Investiga that the characteristics of actinobacteria that can adapt to different conditions “allow them to use different compounds, such as pesticides, as a carbon source. We analyzed the bacteria in the laboratory to see how they acted against pesticides that are no longer used –such as organochlorines–, but that are still present in the soil because they are persistent. For example, we studied their action with soils contaminated with lindane (it was used to combat pediculosis) and with chlordane and methoxychlor (to combat mosquitoes), and we saw that they are capable of reducing their concentration”.

The researcher stated that organochlorines can remain in the soil for several years after they have ceased to be used. She added that before they were widely used due to their low cost and that, for some years, they have been banned or restricted due to their toxicity and persistence. She commented that the bacteria used in the tests were isolated from a clandestine deposit located in an Argentine town of Santiago del Estero, which contained several tons of organochlorine pesticides. “The bacteria isolated from this deposit have the capacity to grow and eliminate organochlorine pesticides. They degrade or break the molecules, until they are not available in the environment”, she pointed out.

Both Bazán and Fuentes commented that they began to test with the herbicide atrazine with very promising results. “We saw that the consortia of these microorganisms generate more metabolic pathways to degrade or remove the polluting agent. Because if I have only one bacterium, it is difficult for it to convert the pesticide into a less toxic compound, but if I have more bacteria, they can cooperate with each other in this degradation pathway; that is why we use the consortium”, they detailed.

Meanwhile, Dr. Bazán specified that they tested atrazine with four different consortia of bacteria, which had previously been tested for organochlorines. “We did this because atrazine has chlorine in its molecule and, although it is not an organochlorine, it does have the atom present. In the tests in liquid media, we saw that these consortia have the capacity to grow and remove atrazine in different concentrations, including the strongest ones”, she specified.

The researcher commented that, after the tests, they analyzed the residual pesticide in a chromatograph and detected a concentration of atrazine 70% lower than the original version. She added that the next step will be to carry out toxicity tests, which involve putting the contaminated and sanitized media in contact with the consortium of bacteria. Then grow plants, eg lettuce, wheat, and tomato, and assess whether the decontaminated medium is less toxic than the untreated medium.

The researchers announced that they began to carry out tests combining the consortium of bacteria with industrial waste (such as bagasse) and household waste (such as disused orange peel and yerba mate), to see if the action of soil sanitation is enhanced. contaminated with pesticides.

Bazán commented, meanwhile, that a double benefit is sought: on the one hand, to give added value to something that goes to the trash and, on the other, to see if it works as a soil biostimulant, “because the residues contain nutrients that stimulate growth of native microorganisms”, he indicated. And the main goal will be to check if the waste improves the metabolism of the consortium of bacteria and thus promotes soil remediation. (Source: National University of Tucumán / Argentina Investiga)