Characterization of lytic enzyme activities of Lactobacillus gasseri with special reference to autolysis

Lactobacillus gasseri JCM 1130 and JCM 1131(T) exhibited autolytic activity in agar containing autoclaved cells of each strain as substrate. By zymogram analysis of JCM 1131(T), two lytic bands with apparent molecular masses of 54.5 and 35 kDa, were detected. Similarly, JCM 1130 yielded two lytic bands with apparent molecular masses of 35 and 33.5 kDa. In simple buffers as well, JCM 1131(T) suffered a drastic decrease in cell turbidity, but JCM 1130 did not undergo the decrease. The optimal pH for autolysis of JCM 1131(T) was in the range of 6.0-7.0, and the lysis was completely inhibited at pH 4-5. The lysis of JCM 1131(T) was suppressed by NaCl, in a concentration-dependent way. When subjected to UV irradiation or mitomycin C (MMC) treatment, cultures of both strains elicited conspicuous turbidity decrease after 2-4 h of growth, suggesting the occurrence of prophage induction. The 35-kDa lytic band of JCM 1131(T) and the 33.5-kDa protein of JCM 1130 were considerably increased by UV irradiation.