This study was carried out by a team of researchers at the University of Caen in France led by Professor Gilles-Eric Seralini. Seralini is a French molecular biologist known for his groundbreaking study that linked genetically modified corn and glyphosate in Roundup to cancer. His findings were so damning that Roundup manufacturer Monsanto took action to have the study retracted, only to see it later republished elsewhere.
In his latest study, fecal samples of rats were analyzed to assess their gut microbiomes. The researchers also grew bacteria in vitro using feces taken from control animals and then treated with three concentrations of Roundup: 0.1 ppb, 400 ppm, and 5,000 ppm.
The study found a sex-specific alteration in the female rats' gut microbiomes. There was a rise in the Bacteroidetes family S24-7, while the Lactobacillae bacteria family noted a decrease. These changes were seen in all three of the Roundup doses given to the rats, which would appear to indicate that the effect is more related to the presence of Roundup in the first place than the amount administered.