Moraxella osloensis is a Gram-negative oxidase-positive, aerobic bacterium within the family Moraxellaceae in the gamma subdivision of the purple bacteria. Moraxella osloensis is a mutualistic symbiont of the slug-parasitic nematode Phasmarhabditis hermaphrodita. In nature, Phasmarhabditis hermaphrodita vectors M. osloensis into the shell cavity of the slug host in which the bacteria multiply and kill the slug.