Pseudomonas aeruginosa is a Gram-negative, aerobic rod, belonging to the bacterial family Pseudomonadaceae. The family includes Xanthomonas, which together with Pseudomonas, comprise the informal group of bacteria known as Pseudomonads. These bacteria are common inhabitants of soil and water.

Pseudomonas mallei causes a disease in horses known as glanders. It is a true parasite, since it is unable to survive in nature in the absence of its host. The primary focus of infection is the lungs. The disease can be transmitted to humans from the horse.