The present paper deals with the studies made on the growth inhibitory action of galactose against the Mutabile-type variants (Murase) of the several kinds of enteric bacteria. Method employed for the preparation of titrating medium is essentially the same as the cup method for the titration of penicillin units. Namely, 0.01ml of galactose solution in varying concentrations is pipetted out onto a paper disk of 6 mm in diameter, and the growth inhibition zone is measured which will be produced around the disk following 24 hours incubation at 37 C.
M-type variants of
E, coli, paracoli-type
E. coli, S. paratyphi A,
S. paratyphi B,
S. typhi-murium, S. typhi, S. enteritidis and
Shigella sonnei were isolated by Murase's method.
Galactose sensitivity test was made on the M-type variants of the following kinds : 1) those derived from a single broth culture, 2) those derived from the same strain but differnt broth cultures, 3) those derived from the cultures once grown on the medium containing galactose, 4) those derived from the strains once grown on the medium containing lactose, 5) those derived from the strains which have never been in contact with galactose, or ldctose, 6) new variants and 7) old rough variants.
Results of the experiment revealed that some of the M-type variants tested were highly sensitive to an extremely small amount of galactose. Namely, some variants showed a growth inhibition zone even at a concentration of 0.8γl, while some failed to show it even at a concentration as high as 1.6γl. This galactose sensitivity of M-type variants appear to have no relation with the difference in the condition of their isolation.
Further, the M-tye variants which have undergone changes being cultured on galactose medium can grow well on ordinary agar medium. Thus, it is believed that the strong growth inhibitory action of galactose on M-type variants appears only when they are grown on the medium containing galactose.
While, the lethal dose of galactose fails to show any appreciable damage on the growth of M-type variants when the cultures are kept in a refrigerator or when they are kept in an incubator for a night on the medium containing no other nutrients. In other words, the bactericidal power of galactose seems to appear in respond to the growth of microorganisms.
Accordingly, the growth inhibition zone around the galactose disk may be produced by the sugar diffusing out of the disk being sharply defined from the area of abundant growth.
抄録全体を表示