Biochemical and biophysical studies of Bacillus subtilis envelopes under hyperosmotic stress

The behaviour and state of the envelopes from B. subtilis cultures grown in Luria Bertani (LB) medium with and without 1.5 M NaCl are compared. Under hypertonic conditions, the hydrophobicity of the cultures increases. The ph ospholipid and fatty acid (FA) compositions show important differences: a h igher cardiolipin (CL) content [at the expense of phosphatidyl-glycerol (PG )], and a higher unsaturated and straight chain FA content. The fluidity of the membranes, determined with fluorescent probes, indicates an increase i n viscosity of the cytoplasmic membrane. The consequences of these variatio ns in membrane permeability and osmotolerance are discussed. (C) 2000 Elsev ier Science B.V. All rights reserved.