The Moraxellaceae are a family of Gammaproteobacteria, including a few pathogenic species. Others are harmless parasites of mammals and humans or occur in water or soil. The species are mesophilic or psychrotrophic (Psychrobacter). Moraxella catarrhalis is a human pathogen, and Moraxella bovis is the cause of "pinkeye" of cattle (infectious bovine keratoconjunctivitis).