New York:Researchers have found that absence of a specific species of gut bacteria can result in an imbalanced microbial ecology, causing social deficits in mice, similar to symptoms of autism spectrum disorders (ASDs) in humans. The findings showed that lack of Lactobacillus (L.) reuteri in the mice born to mothers on a high-fat diet is responsible for their social deficits. Mice born to mothers on the high-fat diet showed more than nine-fold reduction of L.reuteri in their microbiomes. By adding this bacteria species back to the guts of affected mice, the researchers were able to reverse some of their behavioural deficits, which are reminiscent of symptoms of autism spectrum disorders (ASDs) in humans. "We cultured a strain of L. reuteri originally isolated from human breast milk and introduced it into the water of the high-fat-diet offspring. We found that treatment with this single bacterial strain was able to rescue their social behaviour," said lead author Shelly Buffington, postdoctoral researcher at Baylor College of Medicine in Houston, US. However, other ASD-related behaviours, such as anxiety, were not restored by the reconstitution of the bacteria, said the paper published in the journal Cell. Further, L. reuteri was found to promote the production of oxytocin -- the "bonding hormone" -- which plays a key role in social behaviour and has been associated with autism in humans. The socially impaired mice also showed dysfunctional in their brains' reward circuitry. "When we put the bacteria back in the maternal-high-fat-diet offspring, we could also restore the changes in synaptic function in the reward circuitry," Mauro Costa-Mattioli, neuroscientist at Baylor College of Medicine, added. "Whether it would be effective in humans, we don't know yet, but it is an extremely exciting way of affecting the brain from the gut," Costa-Mattioli noted.