胆汁耐性乳酸菌に関する研究

Abstract

1. The bile-tolerant (BT) strain of Lactobacillus was proved almost identical with its parent strain in many properties such as growth, acid production, many physiological properties, and serological aspect.2. However, BT strain differed from the parent strain in several points: It had a tendency of poor coagulation of litmus milk. The increasing order of tolerance to acidity was as follows: BT (2) strain=parent strain>BT (1) strain; to NaCl was as follows: BT (2) strain>parent strain>BT (1) strain; to heat at 65°C in saline was as follows: BT (1) strain=parent strain>BT (2) strain. The increasing order of stability on exposure of freeze-dried cells to 37°C was as follows: BT (1) strain>BT (2) strain>parent strain.3. Drop of tolerance to bile salts did not appear during a year storage of BT (1) strain in cell powder subjected to freeze-drying, or during serial transfer of it to bile free medium even after 10th passage, and its tendency of poor coagulation of litmus milk had been kept.However, the tolerance dropped during a year storage of BT (1) strain in cooked meat medium and its coagulation of litmus milk became positive.Thus, it was considered that both the tolerance to bile salts and the tendency of the poor coagulation of litmus milk were the properties possessed of BT strain and not of its sensitive parent strain.4. The mutation rates seemed to be increased with the raise of bile concentration in the medium for transferring cultures.5. The bile-tolerant (BT) strain of Streptococcus was proved almost identical with its parent strain in many physiological properties, except a tendency of poor coagulation of litmus milk.