beta-D-chloroalanine (200-800 micrograms/ml) addition to Bacillus subtilis SB 19 caused a slight inhibition of growth in MLN broth. Inhibitor plus 1% glycine initiated rapid lysis of cells (complete in 2 hours). D-alanine (500 micrograms/ml) prevented lysis. D-cycloserine behaved similarly. Inhibitors in 0.5 M sucrose and 1% glycine formed stable "primed protoplasts" which were converted to the bacillary form by addition of D-alanine. Characteristics of Dal+ cells with inhibitor are similar to Dal- mutants. Thus Dal+ cells in the presence of alanine racemase inhibitors + glycine can be used for controlled lysis and protoplast formation (suitable for PEG transformation with plasmid DNA). Inhibitors in 1% glycine exhibit a strong antibacterial action similar to potent antibiotics which inhibit cell wall formation.