Final answer:
The green discoloration in pus or sputum is caused by pigments called pyocyanin and pyoverdin, produced by the bacterium Pseudomonas aeruginosa.
Step-by-step explanation:
The green discoloration of pus or sputum seen during common bacterial infections is due to the presence of pigments called pyocyanin and pyoverdin. These pigments are produced by some strains of the bacterium Pseudomonas aeruginosa, which is an opportunistic pathogen known to cause infections in hospital environments and in patients with conditions like cystic fibrosis. Pseudomonas aeruginosa is an aerobic, versatile bacterium that can produce a distinctive blue and yellow pigmentation, which appears green in cultures, and exhibits resistance to many antibiotics.
Pyocyanin and pyoverdin are siderophores involved in the iron uptake that helps the bacterium to thrive in low-iron environments, contributing to its pathogenicity.