Pseudomonas aeruginosa is a highly adaptable "blue-green bacterium" that tends to infect individuals with weakened immune systems. While it rarely causes illness in healthy people, it is a significant source of hospital-acquired infections. This bacterium frequently affects individuals with compromised immune systems, burn victims, and those using catheters or respirators. Infections caused by Pseudomonas can result in bloodstream infections and various other serious health issues. It often colonizes the lungs of patients with cystic fibrosis, contributing to the progression of their chronic lung disease and increasing mortality rates.Pseudomonas aeruginosa is commonly found in soil, marshes, and coastal marine environments. It is capable of surviving in conditions that are inhospitable to most other organisms, thanks to its slime layer that prevents engulfment and its resistance to many antibiotics. This bacterium can thrive in a wide range of environments, such as eyedrops, soaps, sinks, medical equipment, fuels, humidifiers, and even stored distilled water. It has also been detected in dialysis machines. The characteristic color of the pus associated with Pseudomonas infections is due to a bluish pigment called pyocyanin and a greenish pigment produced by the bacterium.In 2000, the complete genome sequence of Pseudomonas aeruginosa was published in the journal Nature (Stover et al., 406:959-964). At the time, it was the largest bacterial genome ever sequenced, consisting of a 6.3-Mbp genome with 5,570 predicted genes on a single chromosome.