The human nasal cavity harbours different opportunistic pathogens. The pathobiont Moraxella catarrhalis colonizes the human respiratory tract and is correlated to the development of respiratory diseases such as asthma and chronic obstructive pulmonary disease. Previous studies have characterized microbial competitive interspecies interactions within the nasal cavity, where one species adopts a strategy (secretion of toxins or antibiotics, iron sequestration, and so on) to kill or prevent the growth of the competitor species. In this study, Stubbendieck et al. found bacterial species that target M. catarrhalis.