COLUMBUS, Ohio – Emerging evidence has long suggested that pesticides can be toxic to the microorganisms residing in our digestive systems. Now, a groundbreaking study has mapped the specific changes to gut bacteria when exposed to various insect-killing chemicals. Conducted in both laboratory settings and animal models, this research is the first of its kind to detail these interactions.
The study revealed that over a dozen pesticides influence the growth patterns of human gut bacteria, affecting how these microorganisms process nutrients and even reside within certain bacteria. Researchers have made this “atlas” of molecular mechanisms publicly available, offering a resource for further studies on diseases and potential therapeutic strategies.
Mapping the Interactions
Experiments conducted on mice highlighted that a particular species of gut bacteria provides some protection against pesticide toxicity. This finding opens the door to the possibility of using probiotics to mitigate some of the harmful health effects of pesticides, such as inflammation.
“We’ve provided further understanding of how pesticides or environmental pollutants impact human health by modulating an important collection of microorganisms,” said Jiangjiang Zhu, associate professor of human sciences at The Ohio State University.
The research, recently published in Nature Communications, examined interactions between 18 commonly used pesticide compounds and 17 species from four major bacterial domains in the human gut. These bacteria are associated with either health maintenance or disease states. Notable pesticides studied include DDT, atrazine, permethrin, and chlorpyrifos.
Understanding the Mechanisms
According to Li Chen, a senior research associate in Zhu’s lab, the team managed over 10,000 samples to analyze how microbes responded to pesticide exposures. This effort led to the development of a bacteria-pesticide interaction network, detailing which pesticides promoted or inhibited bacterial growth and which bacteria absorbed pesticide chemicals.
“Most previous environmental health studies reported that pesticide contamination affects the overall composition of gut bacteria,” Chen said. “We showed those pesticides really can affect specific gut bacteria and detailed how these changes will affect the general composition.”
The study identified specific metabolic changes in 306 pesticide-gut microbe pairs. This led to an examination of how altered growth patterns and chemical accumulation impacted metabolites, the molecular products of biochemical reactions essential for energy production and other functions.
Implications for Human Health
The research team also analyzed the effects of pesticide exposure in healthy mice, first treated with antibiotics to clear their digestive systems of microbes. The introduction of Bacteroides ovatus, a common human gut bacteria, to one group of mice showed that pesticides caused inflammation in multiple organs. The presence of this bacteria after chemical exposure led to changes in metabolic activity and lipid production.
Specifically, an increase in certain lipid classes inhibited the signaling pathway of a protein linked to oxidative stress, suggesting that certain microbes might modulate the toxic effects of pesticides by buffering the inflammation process.
“We know inflammation is generally bad for the body. If something toxic is going to induce it, and there are other molecules that can counteract that agent, you may have a solution to intervene or prevent larger-scale damage,” Zhu explained.
Future Research Directions
Looking ahead, Zhu’s lab plans to further explore how metabolic changes in gut microbes fit into various health and disease conditions following pesticide exposure. The team anticipates that other scientists will build upon their findings to predict targets or identify intervention strategies.
“We are mapping out this central interaction between pesticides and gut microbes. Other labs can leverage what we have discovered to contribute to disease research and eventually help with predicting targets or identifying an intervention strategy,” Zhu said.
This research was supported by the National Institute of General Medical Sciences, with additional support from the Provost’s Scarlet and Gray Associate Professor Program at Ohio State. The study’s co-authors include experts from Ohio State, Yale University, Zhejiang Academy in China, and Johns Hopkins University.
