1959 Volume 19 Issue 6 Pages 541-553
Mutabile-type variants (Murase) were isolated from each of E. coli, paracoli-type E. Pcoli, so-called paracolon Aerobacter and Lactose variant of the latter two. Their galactose and lactose sensitivity were tested by the paperdisk method devised by the author's laboratory. Experimental results obtained were as follows :
Mutabile-type variant of E. coli and that of lactose variant of the lactose slow fermenters equally gave growth inhibition zone in such a concentration of galactose as 0.87-1.6γ and of lactose as 3.1γ—6.3γ.
Mutabile-type variant of paracoli-type E. coli, though sensitive to galactose like those mentioned above, gave no inhibition zone by lactose in a concentration as high as 10, 000γ, except that 1/23 of paracoli-type E. coli and 5/5 of paracolon Aerobacter both of which gave some incomplete inhibition zone by lactose in a concentration of 100γ—1, 600γ. Their Mutabile-type variants, however, were very sensitive to lactose if they had originated from the Lactose variants derived from the original form.
It is belived, therefore, that when a Mutabile-type variant is derived from the E. coli of Lactose fermenting form, it possesses the charactors inherited from its mother cell. Thus, it seems that lactose is fermented first and galactose is freed from it acting on Mutabile-type variants as if free galactose is added from the beginning. Therefore, the growth inhibitory action of lactose appears strongly on Mutabile-type variants.
