NUTRITIONAL STUDIES ON THE “AUTO-PLAQUE” PHENOMENON IN PSEUDOMONAS AERUGINOSA

Berk, Richard S. (Wayne State University, Detroit, Mich.). Nutritional studies on the “auto-plaque” phenomenon inPseudomonas aeruginosa . J. Bacteriol.86: 728–734. 1963.—Examination of 20 cultures ofPseudomonas aeruginosa indicated that 18 cultures possessed the common property of spontaneously lysing to form “plaques” or erosions on themselves in the absence of a sensitive indicator strain. Maximal lysis and plaque production was found to occur on a medium with a Tryptone concentration of 2.0 to 2.5%. Reduction of the Tryptone concentration to 0.5% or less supported growth, but was usually inadequate for support of lysis. However, addition ofl -asparagine orl -arginine to 0.5% Tryptone induced lysis. Examination of five strains ofPseudomonas , which routinely exhibited the autolytic phenomenon, indicated that all were both lysogenic and pyocinogenic when tested against otherPseudomonas strains on both 2 and 0.5% Tryptone. Culturing of autolytic strain Pa-1 on a simple medium composed of glucose and inorganic salts appeared to be inadequate for “auto-plaque” formation, although lysis occurred occasionally when a yeast extract concentration of 1% was incorporated into the medium. Suppression of auto-plaque formation was also effected by growing the culture on Technicon dialyzing membrane D3 overlaid on 2% Tryptone, although lysogenic lysis of an indicator strain was demonstrable on the membrane.