Genetic engineering creates alternative to chemical pesticides

By Joan Conrow

March 5, 2019

Researchers at Cardiff University in Wales have used genetic engineering to repurpose a strain of beneficial bacteria for use as a safe, sustainable alternative to chemical pesticides.

The research team found that Burkholderia ambifaria bacteria, when altered with genomic tools, have the potential to act as effective biopesticides, replacing synthetic pesticides that can harm human and environmental health.

“Through our work, we hope to make Burkholderia viable as an effective biopesticide, with the ultimate aim of making agriculture and food production safer, more sustainable and toxin-free,” said lead researcher Eshwar Mahenthiralingam of Cardiff University’s School of Biosciences.

“Beneficial bacteria such as Burkholderia that have co-evolved naturally with plants have a key role to play in a sustainable future,” Mahenthiralingam said. “We have to understand the risks, mitigate against them and seek a balance that works for all.”

This isn’t the first time that biopesticides have been eyed for crop protection.

Though the group of bacteria called Burkholderia successfully protected crops against diseases, in the 1990s they were linked to serious lung infections in people with cystic fibrosis (CF), leading to concerns about their safety. They were eventually taken off the market.

This experience led scientists into other fields of research.  “I have been working with Burkholderia for many years, primarily in relation to CF lung infections, which in turn led to a new line of antibiotic discovery research,” Mahenthiralingam said.

He then teamed up with plant scientist Jim Murray, who heads the School of Biosciences, and doctoral student Alex Mullins to investigate Burkholderia-plant interactions and how they protect plants against disease.

“By sequencing the genomic DNA of the bacteria, we were able to identify Burkholderia‘s antibiotic-making gene, Cepacin,” Mahenthiralingam said in a university press release. “Further testing demonstrated that Cepacin offered highly effective protection against damping off — a horticultural disease caused by a fungus-like organism.”

Using genetic engineering techniques similar to those used to produce live vaccines, the researchers are also exploring how to improve the safety of the bacteria.

Burkholderia split their genomic DNA across three fragments, called replicons,” Mahenthiralingam explained. “We removed the smallest of these three replicons to create a mutant Burkholderia strain which, when tested on germinating peas, still demonstrated excellent biopesticidal properties.”

Further work showed that this Burkholderia mutant did not persist in a mouse lung infection model, opening up the possibility of constructing biopesticidal strains that can still deliver effective plant protection without the risk of causing infection.

Their research is published in Nature Microbiology.

The Cardiff University team, working in collaboration with chemists Greg Challis and Matthew Jenner of the University of Warwick, recently were awarded a £1 million grant from BBSRC to take the research to the next level. The goal is to develop an effective and safe biopesticide that does not build up to harmful levels in the environment.