GELATINOUS VARIANTS OF PSEUDOMONAS AERUGINOSA

Abstract

A new variant of P. aeruginosa has been identified. It is characterized by the production of exceedingly large jelly-like colonies when grown on media containing glycerol. The variation seems to consist wholly of ability to produce large amts. of gelatinous material and to be entirely independent of other variations exhibited by this organism. The gelatinous material appears to be a carbohydrate. Similar gelatinous colonies are produced by the variant when it is grown in the presence of certain alcohols other than glycerol, and in the presence of certain oils or fats. However, the nature of the material produced on these latter substrates has not been compared chemically with that produced on glycerol. The variation appears to be wholly physiol. and may be superimposed on any of the basic colony types of the organism. The variant is in the main stable, but some reversion to ordinary nongelatinous colonial forms does occur, especially when it is grown for a time in fluid media free of glycerol. The nongelatinous colonies which then appear usually correspond topographically to the gelatinous forms except for the absence of the gelatinous material. The gelatinous forms show about the same range of variation in pigment production observed in ordinarily nongelatinous colonial forms. They are, moreover, not distinguishable from ordinary nongelatinous forms on the basis of serological or phage-suscep-tibility tests. Sections prepared from large gelatinous colonies show that the material in these colonies consists primarily of gelatinous material, with relatively few organisms irregularly distributed through the material. It seems probable, however, that the material is synthesized primarily by organisms located next to the medium and that most of the organisms found in the upper strata have been carried upward as the material is produced. The consistency of the gelatinous material produced varies to some extent among different gelatinous clones. Although like a stiff jelly as a rule, it may be relatively thin or watery in the case of certain clones. It is, however, in no sense viscid and is therefore not to be confused with a mucoid type of variation. Although this particular variation appears to be of infrequent occurrence, media containing glycerol have probably been rarely employed in the initial isolation of the organism from infected lesions. However, in addition to the variant originally isolated from an infected lesion, a similar variant has been from a stock strain being carried on a glycerinated medium.