Surprising discovery: Germs punish 'black sheep' and enforce fairness principles within their communities

Bacteria can have the behavior of "spitting" on misbehaving siblings, a study has shown. Annoyed by freelancers? You are not alone, taking advantage of others is a problem that affects all species, not just humans. In fact, such selfish behavior is not uncommon in the animal kingdom, and even cheating bacterial species exhibit it. A more intriguing fact has been revealed by a research team led by the University of York, which investigated the quorum-sensing properties of bacteria, a complex type of cooperation that allows bacteria to regulate gene expression according to population density. Researchers from Case Western Reserve University and York University collaborated on the study, which was recently published in the journal PLOS Computational Biology. They were surprised to find that bacterial communities can harm themselves in order to get rid of advantaged individuals. Associate Professor Andrew Eckford, from York University's Lasunder School of Engineering and senior author of the study, said: "We didn't expect to see this kind of behaviour, it might even be called 'spitting'. But it shows that having quorum sensing capability is a very flexible tool for enforcing equity." In this study, the scientists investigated how quorum sensing mechanisms regulate the supply of shared resources, such as converting food sources into useful nutrients substances of enzymes. When thieves stole nutrients without creating enzymes, they found that thieves were punished even if the entire community was affected, similar to the practice of announcing the cancellation of a feast when an unwelcome visitor sneaks in. Furthermore, if free food is common and no other food is available, this mechanism may starve the entire population. "Contributing to the community is expensive for a bacterium, so for a selfish individual it is better to simply accept what is offered without giving anything in return," explains lead author Alex Moffett. He was a postdoctoral researcher at York University at the time of his research. "But obviously it's not good for every bacterium, so the community needs a way to stop bad behavior." Moffitt and his colleagues found that instead of relying on an "honor system," the microbes used quorum-sensing way to suppress slackers. To further understand how swarm sensing compares with other strategies for controlling the production of public goods, they used mathematical modelling. "Our model captures both 'cheating' strains -- which don't produce public goods but are Benefit -- the possibility of taking over a population, also captures how long the population lasts on average before going extinct." Since quorum sensing plays an important role in bacterial infections, such as those affecting the lungs of cystic fibrosis patients, The research team hopes to apply the findings of this study to understand and disrupt such diseases. "This will help us understand how bacteria can colonize the lungs so efficiently, which could point the way to new treatments," Moffett added. "