Microorganisms do not just colonize the body of mammals during infections. Billions of microbes can be found on and in healthy humans and animals at any given time, communicating with each other via chemical signals and thus influencing their health. In two studies, researchers have now conducted a detailed study of the microbiome, i.e. the totality of all microorganisms, in humans and zoo animals. The aim was to identify starting points for strategies for the treatment and diagnosis of diseases.