Relationship of critical micelle concentrations of bacterial lipoteichoic acids to biological activities.

The critical micelle concentration (CMC) of lipoteichoic acid (LTA) was investigated with two dyes, rhodamine 6G and Coomassie brilliant blue R-250. Both dyes gave similar values for the CMC of LTA. The CMC of LTA from several species of bacteria ranged from 28 to 60 micrograms/ml in phosphate-buffered saline. The CMC values for the LTAs are in the range expected for an amphiphile containing a single, 16-carbon fatty acid residue. Formation of micelles was not detected with deacylated LTA. Salt decreased the CMC of LTA from 380 micrograms/ml in distilled water to 37 micrograms/ml in 0.5 M NaCl. At concentrations greater than the CMC, LTA induced the lysis of sheep erythrocytes and was cytotoxic for Girardi heart cells. The data suggest that LTA in the micellar state may cause disruption of the erythrocyte membrane and may be cytotoxic for cells in culture.