All members of the Pseudomonas fluorescens group are noted for producing which pigment?

• A. Pyomelanin
• B. Pyocyanin
• C. Pyoverdin
• D. Pyorubrin

Answer: (C)

Fluorescence is the clue here. The Pseudomonas fluorescens group is known for producing pyoverdin, a yellow-green pigment that fluoresces under UV light. Pyoverdin is a siderophore the bacteria secrete to grab iron from the environment, which also explains why these organisms often look glowingly bright under UV on appropriate media. This fluorescence is a hallmark used to identify fluorescent pseudomonads in the lab. Other pigments, like the blue pyocyanin produced by Pseudomonas aeruginosa or brown-black pigments such as pyomelanin, are not characteristic of the Pseudomonas fluorescens group, so pyoverdin is the best answer.