Characteristics of pathogenic non-fluorescent (smooth) and non-pathogenic fluorescent (rough) forms of Pseudomonas tolaasii and Pseudomonas gingeri

Pseudomonas tolaasii and Ps. gingeri cultures isolated from naturally diseased mushrooms and cultures obtained from other workers were all observed to contain both smooth and rough colony forms. The smooth forms produced mucoid, non-fluorescent, glistening opaque colonies with entire margins. The rough forms produced non-mucoid, fluorescent, dull, translucent greenish-yellow colonies with irregular margins. Smooth forms were observed to produce a toxin and were pathogenic to mushrooms, whereas rough forms did not produce toxin and were non-pathogenic. Isolates of Ps. tolaasii were distinguishable from Ps. gingeri by various biochemical tests. In general, however, biochemical differences between the rough and smooth forms of each species could not be detected. Rough forms of Ps. tolaasii and Ps. gingeri remained stable in culture but smooth forms were unstable, tending to convert to rough forms at a very high rate.