Membrane lipid composition of Bacillus stearothermophilus as affected by lipophilic environmental pollutants: an approach to membrane toxicity assessment.

The thermophilic eubacterium Bacillus stearothermophilus is used as a model to identify membrane perturbing effects of lipophilic compounds. A parallelism has been established between the toxicity of the organochlorine insecticide DDT and its metabolite, DDE, in bacterial growth and the effects on cell functions and physical perturbations induced at the membrane (Donato et al. 1997a, Arch Environ Contam Toxicol 33:109-116; Donato et al. 1997b, Appl Environ Microbiol 63:4948-495). In the present work, the use of B. stearothermophilus as a model of screening for chemical toxicity has been implemented. Because the regulation of the lipid composition of the membrane is a common strategy in response to adverse growth conditions, we studied the effects of DDE on the lipid composition and the consequent alterations of membrane physical properties in comparison to the parental compound DDT. As expected, different adaptation responses were induced by the compounds, being DDT more effective as compared with DDE. Collected data are consistent with the stronger perturbations induced by DDT on growth and membrane functions. It is concluded that the membrane lipid composition of the bacterium is a very sensitive criterium to detect membrane-mediated toxic effects at low concentrations of lipophilic xenobiotics.