Pseudomonas Aeruginosa - Identification

Identification

It is a Gram-negative, aerobic, coccobacillus bacterium with unipolar motility. An opportunistic human pathogen, P. aeruginosa is also an opportunistic pathogen of plants. P. aeruginosa is the type species of the genus Pseudomonas (Migula).

P. aeruginosa secretes a variety of pigments, including pyocyanin (blue-green), pyoverdine (yellow-green and fluorescent), and pyorubin (red-brown). King, Ward, and Raney developed Pseudomonas Agar P (King A medium) for enhancing pyocyanin and pyorubin production, and Pseudomonas Agar F (King B medium) for enhancing fluorescein production.

P. aeruginosa is often preliminarily identified by its pearlescent appearance and grape-like or tortilla-like odor in vitro. Definitive clinical identification of P. aeruginosa often includes identifying the production of both pyocyanin and fluorescein, as well as its ability to grow at 42°C. P. aeruginosa is capable of growth in diesel and jet fuel, where it is known as a hydrocarbon-using microorganism (or "HUM bug"), causing microbial corrosion. It creates dark, gellish mats sometimes improperly called "algae" because of their appearance.

Although classified as an aerobic organism, P. aeruginosa is considered by many as a facultative anaerobe, as it is well adapted to proliferate in conditions of partial or total oxygen depletion. This organism can achieve anaerobic growth with nitrate as a terminal electron acceptor, and, in its absence, it is also able to ferment arginine by substrate-level phosphorylation. Adaptation to microaerobic or anaerobic environments is essential for certain lifestyles of P. aeruginosa, for example, during lung infection in cystic fibrosis patients, where thick layers of lung mucus and alginate surrounding mucoid bacterial cells can limit the diffusion of oxygen.