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For more than a decade, millions of bees around the world have been dying mysteriously. This week, scientists may have found another clue: tying Roundup, a popular herbicide, to the problems of the bee microbiome.
Past research has linked bees to common pesticides, pests and pathogens, as well as global climate change. According to a new study published this week in Glyphosate magazine, the active ingredient in Roundup could help improve the balance of healthy bacteria in the intestines and make them more vulnerable to disease. Proceedings of the National Academy of Sciences.
"There are many factors responsible for the death of hives related to colony collapse syndrome, and we want to know what is causing it," says Erick Motta, a student at the University of Texas at Austin and author of the new study.
Glyphosate does not actually kill bees. Roundup is a herbicide rather than a pesticide, which means that it is specifically formulated to kill plants, not animals or insects. It is mainly used to kill weeds and other unwanted plants in gardens, yards and agricultural fields – many genetically modified crops (GM crops) are designed to resist glyphosate rains and other agrochemicals. The product works by stopping the activity of a particular enzyme that exists in all plants and in certain microorganisms.
But just like humans, bees have a community of bacteria living in their digestive tract, called a microbiome. Some of these microorganisms contain the same enzymatic targets as glyphosate.
To examine the microbiome of Roundup bees, Motta took 2,000 bee hives from the University of Texas campus and gave them either a low dose of glyphosate, a high dose, or a syrup without glyphosate. The two dosages of glyphosate are similar to the quantities generally sprayed on the yards, agricultural fields and roadsides. Motta then released the bees and took 15 samples from each group before and after three days in the hive.
In sampled bees, some intestinal bacteria, such as Gilliamella apicola, actually increased in number. Others, like Snodgrassella alvi, have declined. Overall bacterial count decreased for both groups of exposed bees, but the change was statistically significant only for the lowest dose group. Motta is not sure why, but one possibility is that her sampling method did not take into account dead or abandoned bees. Previous research has shown that glyphosate can interfere with bees' ability to navigate. It is therefore possible that more bees at the high dose could never be tested.
Glyphosate seems to affect more Snodgrassella alvi, a dominant bacterium in the intestine of honey and bumblebees, than other microorganisms. This bacteria helps regulate the immune response, says Motta. Although researchers do not know exactly how the microbe works, it is possible that a biofilm that the species creates inside the small intestine of the bee physically blocks the pathogens.
Next, the scientists wanted to see if this bacterial change had an impact on the immune response of the bees. This time, Motta brought young bee workers who had not yet developed a normal bacterial community in their bowels. He fed a group of glyphosate and then exposed all the bees to an opportunistic foraging agent.
After a week, more bees exposed to glyphosate and the pathogen died than those exposed only to the pathogen. "Bees with a normal microbial community have been better able to cope with the disease," says Motta.
"This could explain, at least in part, why bee colonies in countries that allow GM crops are becoming weaker and with lower probabilities of survival at the end of the season," Walter Farina writes. in an email to: Popular science. Farina is a biology scientist who studies communication with bees at the University of Buenos Aires and has not participated in the Austin UT study.
Monsanto, the company that makes and sells Roundup (and genetically engineered seeds designed to withstand its effects), says its research has found no evidence of glyphosate harmful to bees. In a statement by email to Popular scienceThe company said: "The claims that glyphosate has a negative impact on bees just are not true. More than 40 years of solid and independent scientific evidence show that this poses no unreasonable risk to humans, animals and the environment in general.
The bee microbiome is a new field of study, says Amro Zayed, a biologist specializing in bees and genomics at York University, who was not involved in the new research. "The authors eloquently show that [glyphosate] does not directly affect the biology of bees, "he says," but it affects this community of bacteria that live in the digestive tract of bees, which digest nutrients and fight infections. "
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