PIGMENTATION VARIANTS OF PSEUDOMONAS AERUGINOSA.
Howarth, S. (University of Otago, Dunedin, New Zealand), and M. D. Dedman. Pigmentation variants of Pseudomonas aeruginosa. J. Bacteriol. 88:273-278. 1964.-Pigmentation variants were isolated from Pseudomonas aeruginosa strain 1, including both FP(+) and FP(-) sublines, and strain 78 by growth with sulfathiazole. The changes were from the normal yellow-green color to brown and nonpigmented variants. Brown variants arising from strain 1 were studied in most detail, and were found to occur as spontaneous mutants in the normal population with a frequency of about 10(-7). These variants have other altered characteristics; notably, they show a change to a smooth colony morphology and resistance to the virulent bacteriophage E79. When grown in the presence of sulfathiazole, pigmentation variants have a selective growth advantage, which would account for their presence in unusually high numbers in populations surviving sulfathiazole treatment.