抄録
Mutabile-type variant Murase (M), its daughter mutabile-type variant (MT), galactose fermenting daughter (RT) etc. were isolated from the original (O) of a para-colon type E. coli and its lactose fermenting variant (V) . The pure culture of each strain was inoculated into B.T.B. lactose peptone water and was incubated for 2 weeks. The daily charge in pH was persued. As the result, the following facts were elucidated.
O→V or ORT→ORTV variation occurred fairly constantly after 4-5 days' incubation. Further, the patterns of these variations were found difficult to distinguish from each other.
OM and OMT did not cause the yellow change in pH.
V or VRT fermented lactose as strains of ordinary E. coli do. Later, they made the culture medium alkaline.
VM or VMT fermented lactose in 4-5 days as if they became para-colon type organisms. Furthermore, VMT→VMTV' variation was observed. VMTV' fermented lactos as V or VRT did. However, the medium became alkaline earlier in the case of VMTV' than in the case of V or VRT.
O, ORT, V and VRT fermented galactose, while OM, OMT, VM, VMT or VMTV' did not.
As stated in the above, (I) this E. coli of para-colon type changed its lactose fermentation formula in the galactose fermenting state as well as in the galactose non-fermenting state, (II) the mutabile-type variant returned to the original type in its galactose fermenta-tion capacity as well as in its lactose fermenting capacity.
