D-Alanyl-lipoteichoic acid in Lactobacillus casei: secretion of vesicles in response to benzylpenicillin

SUMMARY: Vesicles containing lipoteichoic acid (LTA) have been isolated from Lactobacillus casei ATCC 7469 grown in the presence of either benzylpenicillin or D-cycloserine. These cell wall antibiotics enhanced the rate of LTA and lipid secretion 6.7 times, whereas chloramphenicol inhibited their release. The formation of these vesicles from peripheral and septal wall regions did not appear to be the result of bacteriolysis. The vesicle composition of LTA and lipid was similar to that of the cytoplasmic membrane whereas the protein composition was dissimilar. The size of these vesicles ranged from 20 to 40 nm and the length of LTA ranged from 5 to 50 glycerol phosphate residues. The isolation of these vesicles provides a potential in vitro acceptor system for studying the D-alanylation of lipoteichoic acid.