DETECTION OF PSEUDOMONAS COLONIES THAT ACCUMULATE POLY-BETA-HYDROXYBUTYRATE ON NILE-BLUE MEDIUM

A simple procedure was developed to detect colonies of bacteria that a ccumulate poly-beta-hydroxybutyrate (PHB), a storage product character istic of many nonfluorescent pseudomonads. Colonies of PHB-positive ba cteria fluoresced bright orange to yellow under long-wave ultraviolet light when grown on a medium containing PHB and Nile blue dye. Bright orange fluorescent granules were visible within the cells when examine d microscopically under ultraviolet light. Colonies of fluorescent pse udomonads did not fluoresce on this medium, nor were fluorescent granu les visible microscopically. This technique allows detection of PHB-po sitive pseudomonads without microscopic examination. Nile blue medium also was useful as a differential isolation medium for Pseudomonas sol anacearum and may be useful for other nonfluorescent pseudomonads.