A biological mechanism of bacteria has been shown to target a common milk protein, supporting infection spread and persistence. Bacteria that are a major source of infection are able to survive and persist in dairy cattle by releasing nutrients from milk, researchers have shown.The bacteria, Staphylococcus aureus, which causes widespread human disease and is a leading cause of mastitis in dairy cows, has undergone key metabolic changes that help it survive in the udder, Roslin scientists found.The team found that after S aureus moved from humans into cattle, the bacteria evolved ways to access the nutrients available in milk.By identifying the biological mechanisms bacteria use to unlock nutrients, the research shows how S. aureus generates the resources needed to sustain infection in the udder.The findings highlight potential ways to control mastitis in dairy cattle, such as targeting pathways important for growth.Dairy adaptationUsing genetic analyses of bacterial strains recovered from affected people and cows, the team investigated how Staphylococcus aureus adapted to life in dairy cattle.Bacteria that can move between species are a major source of emerging infectious diseases, yet little was previously understood about how S. aureus made the transition from humans to cattle.Bacteria infecting cattle have evolved an enhanced ability to break down casein, the most abundant protein in milk, allowing the bacteria to thrive in the udder and access the nutrients that supports their growth.This process is driven by increased expression of aureolysin, a bacterial enzyme that breaks casein into fragments, which can then be used as nutrients for growth during infection.Infection controlThe findings suggest that the same strategy has evolved independently in several bovine strains of S. aureus, highlighting strong evolutionary pressure that helps explain the bacteria’s ability to adapt to different environments and infect multiple species.Understanding these adaptive changes could also point to new ways of controlling infections such as mastitis in livestock.The study was published in Science Advances and supported by the Biotechnology and Biological Sciences Research Council (BBSRC) and the Wellcome Trust. Understanding how pathogens adapt after jumping between species is crucial for tackling infectious disease. Our research provides a clear example of how genetic changes can promote the successful transition to a new species. Dr Amy Pickering, BBSRC Fellow, the Roslin Institute By understanding the mechanisms underpinning successful host-adaptation, we can start to think about novel ways to control infection. These findings provide insights into where future treatments could intervene. Professor Ross Fitzgerald, Professor of Molecular Bacteriology, the Roslin Institute Related linksResearch publication The Roslin Institute receives strategic investment funding from the Biotechnology and Biological Sciences Research Council and it is part of the University of Edinburgh’s Royal (Dick) School of Veterinary Studies. Tags News Roslin Publication date 11 Feb, 2026
