<i>Lactobacillus plantarum</i>におけるメリビオース代謝の高温感受性機構の解析

Abstract

L. plantarum can grow on melibiose when incubated at 30°C but not when incubated at 37°C. In this study, the temperature sensitivity of melibiose metabolism was analyzed. The melibiose metabolism seemed to consist of the melibiose transport system and hydrolyzing enzyme, α-galactosidase. α-Galactosidase was induced with melibiose at 30°C but not at 37°C. This enzyme induced at 30°C hydrolyzed colorimetric substrate, α-ONPG at 30°C and 37°C. On the other hand, lactose induced α-galactosidase at both temperatures. These findings suggested that the temperature sensitivity of melibiose metabolism was not due to the induction and/or function of α-galactosidase.Thus, the effect of temperature on induction and function of the melibiose transport system was examined. Cells grown on melibiose at 30°C exhibited the rapid uptake of [3H] -melibiose at 30°C and 37°C, while [3H] -melibiose was not taken up by the cells grown at 37°C. The induction of the melibiose transport system seemed to be temperature-sensitive because the transport system was not inactivated by exposure of the cells to 37°C for 3 hours. In conclusion, the temperature sensitivity of melibiose metabolism was attributed to the temperature sensitivity of the induction of melibiose transport system.