Plasmids, small genetic elements that exist outside of chromosomes, are the subject of a new study. A team led by Prof. A. Murat Eren from the Carl von Ossietzky University of Oldenburg has discovered that a certain plasmid is one of the most common genetic elements in the human intestine. With a prevalence of over 90 percent in people in industrialized nations, it could be used as a biomarker for various applications, including the identification of faecal contamination or the monitoring of inflammatory bowel diseases.