VARIATIONS OF THE ENVELOPE COMPOSITION OF BACILLUS-SUBTILIS DURING GROWTH IN HYPEROSMOTIC MEDIUM

The envelope properties of B. subtilis cultures grown in LB and LBN hy perosmotic media (LB + 1.5 M NaCl) were compared. Since hypertonic cul tures showed a Spo-phenotype, a Spo-mutant grown in LB was also analyz ed. LBN cultures showed extensive filamentation and presented differen t sensitivities toward phage infection (phi 29 and phi 105), or antibi otics whose targets are at wall (lysozyme, penicillin G) or membrane l evel (polymyxin B, phosphonomycin). Results of the biochemical composi tion revealed that during hyperosmotic growth, the cell wall increased in thickness, and among the membrane lipids, glycolipid and cardiolip in increased in parallel with a decrease in phosphatidylglycerol. The fatty acid composition was also modified, and an increase in saturated straight chain with a decrease of saturated iso-branched fatty acids was observed. The increase of monounsaturated 18-1 (omega-9) fatty aci d was probably related to the absence of sporulation observed in hyper tonic media, since its increase has been shown to inhibit the KinA sen sor of sporulation. The significance of the other wall and membrane co mposition variations (and hydrophobic surface properties) in relation to the osmotic adaptation are discussed.