Study: Proteins from GM plants capable of reducing E.coli in food

A new study is showing that proteins known as colicins, which are produced by genetically modified plants, can be extracted and applied to contaminated meat and produce to kill harmful E. coli bacteria.

Recently published in the Proceedings of the National Academy of Sciences, the research team engineered tobacco, leafy beets, spinach, chicory and lettuce to produce colicins. In the study, the colicins were then sprayed on E. coli-laced pork steaks, and significant reductions in E. coli were found after just an hour.

The team also hired a third party to do an economic analysis of their process and found that the method competes with decontamination methods, such as acid washes and heat processing, currently favored by the meat industry.

“All of the food outbreaks that have been recorded in the last 15 years or so could have been controlled very well by a combination of just two colicins, applied at very low concentrations,” Yuri Gleba, one of the authors of the study said in a recent article. He added that colicins are 50 times more active against bacteria than normal antibiotics.

As stated in the article, most E. coli in food is found in contaminated beef and pork, but an increasing number of infections have been linked to organic produce, which is typically grown with animal manure in place of chemical fertilizers. According to the World Health Organization, up to 10% of E. coli infections could lead to life-threatening disease.

What exactly are colicins? As explained in the article, they are proteins naturally produced by E. coli strains to kill or inhibit the growth of competing E. coli strains. The proteins are extremely toxic—so toxic, in fact, that engineering microbes to produce colicins usually ends up killing the hosts. To get around that problem, the study’s authors decided to engineer plants since colicins are not as toxic to plant cells. They were successful at getting various plants to express large amounts of 12 different types of colicins, all of which were compositionally identical to colicins found naturally in E. coli.

“Normally the meat industry’s ready to spend two to five cents to treat one pound of meat,” Gleba said. “Our costs are lower than that.”

Furthermore, Gleba believes their process is superior because, unlike heat and acid treatments, colicins do not affect the quality and taste of the meat. Next, the scientists plan to seek approval from the U.S. Food and Drug Administration (FDA) for the process to be considered “generally recognized as safe” (GRAS).

Francisco Diez-Gonzalez, a food safety microbiologist at the University of Minnesota, warned in the article that the FDA’s approval could take a long time.

“To get approval for a food additive, you have to present a lot of toxicology studies and effectiveness studies,” he said in the article. “I think it would be difficult to make the case that these colicins should qualify for GRAS because they’re not typically part of the human diet.”

Other types of bacteria besides E. coli can be killed with colicins, and research team members are planning to extend their process to these next.

“We are already studying colicins for the control of Salmonella,” Gleba added.

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