The effects of commercial grade pluronic F-68 or its purified fraction or Triton X-100 on growth of microbial cells in culture have been studied. Growth of Saccharomvces cerevisia , as determined by viable cell counts, was unaffected by culture with 0.1 10.0% (w/v) of commercial grade pluronic F-68 or its purified fraction. However, cultures treated with 10.0% (W/V) commercial grade or purified pluronic F-68 showed significantly reduced absorbance up to the onset of the stationary phase of growth, as compared to controls. The responses to pluronic F-68 varied according to concentration, age and purity of surfactant. Additionally, the storage temperature influenced the properties of pluronic F-68. Growth in the presence of up to 10.0% (w/v) commercial or purified pluronic F-68 had no effect on cell-associated protein concentration. However, a slight, but reproducible, increase in protein concentration was observed during the exponential/stationary phase in cultures supplemented with 0.1 1.0% (w/v) Pluronic F-68. In addition, whole cell polypeptide profiles were unaffected by the presence of pluronic F-68. \ Triton X-100 altered growth kinetics, as reflected by an extended stationary phase and a slowing of the senescence phase. Additionally, in cultures supplemented with Triton, cell-associated prote in concentration was proportional to cellular growth. culture in the presence of Triton X-100 did not alter the polypeptide profiles characteristi'c of untreated cells at different phases of growth. The application of surfactants for cell permeabilization was also studied using bath Pluronic F-68 and Triton X-100, together with Pluronic F-38 and Pluronic L-35. Permeabilization was assayed by direct measurement of alcohol dehydrogenase (ADH) activity in whole cells. Mean ADH activity following incubation of S.cerevisiae with 0.2% (w/v or v/v) of either commercial or purified Pluronic F-68, Pluronic F-38, Pluronic L-35 or Triton X-100 for 30 min at 20OC was significantly greater than when cells were exposed to an identical concentration of the previously studied permeabilizing agent, cetyltrimethylammonium bromide (CTAB). Maximum permeabilization occurred in the presence of 0.2% (v/v) Triton X-100, and ADH activity following permeabilization with 0.1% (w/v) CTAB plus 0.1% (w/v or v/v) of either commercial or purified Pluronic F-68, Pluronic F-38, Pluronic L-35 or Triton X-100 was consistently less than or similar to that obtained when each compound was used alone. Pre-growth of . cerevisiae for up to 24 h with 0.1% (w/v or v/v) of commercial or purified Pluronic F-68 or Triton X-100 prior to exposure to 0.2% (w/v) CTAB increased the mean ADH activity to a maximum of 49% abave that measured in cells pre-grown in medium alone prior to ermeabilization. \ Pluronic F-68 and Triton X-100 enhanced the sensitivity of . cerevisiae to sub-lethal doses of the antibiotics, cycloheximide (CXM) and amphotericin B (Amp-B). In an extension of these experiments, bath Pluronic F-68 and Triton X-100 similarly potentiated the antibiotic actions of ampicillin (AMP) and chlorhexidine (CLHX) on Escherichia ?Qli. The results are discussed in the context of existing of non-ionic surfactants as microbial membrane-permeabilizing agents. Furthermore, consideration is given to the biotechnological use applications of the Pluronics as cell- rotecting/growth-enhancing media supplements.