一大腸菌のムタビール型変異 (村瀬) 菌よりガラクトース分解性菌の出現上見られた一見パラドツクスな現象に就いて

抄録

Strains of the mutabile type variant according to Murase (M-type variant) were obtained by cultivating E. coli 0-15 for a long period of time in broth.
By cultivating this variant in the galactose peptone water (GP water), a strain of galactose fermenter with acid and gas was obtained. This strain is considered to confer with the strain reported by Kijima as a galactose fermenting daughter type variant (tentatively named) obtained from the M-type variant.
When this M-type variant grown on the galactose fuchsin agar (G. E.) or on the Endo's agar (E) was inoculated in the GP water, almost no fermentation of galactose was observed, but numerous colonies were found fermenting galactose when the organisms was transplanted from ordinary agar to the GP water. Since the above fact is a peculiar mutation phenomen, on the following investigations were conducted to clarify the cause of this phenomenon.
The M-type variant grown on G. E. or on E. also fermented galactose to such an extent that no difference can be noted from the galactose fermentation in the GP water by the M-type variant grown on ordinary agar, when it was grown in the peptone water containing galactose and glucose equivalent to the constitution of lactose, or in the peptone water containing galactose, glucose and fructose equivalent to the constitution of raffinose.
When the M-type variant, grown on the ordinary agar containing galactose to the amount of 0.01%-0.05%, was inoculated in the GP water, only very few colonies were found to ferment galactose. On the other hand, many colonies were found fermenting galactose in the GP water in the experiment with ordinary agar containing 0.5%-5.0% raffinose.
Bacterial suspensions were made from various colonies grown on E. and on ordinary agar with physiologic saline, and decimal dilutions were made from each of the suspensions. Most part of each of the dilutions was inoculated into several tubes of GP water and remaining part of them was inoculated as deep layer cultivation for the purpose of bacterial count. In the cases of the M-type variant derived from ordinary agar, the fermentation of GP water was mostly recorded in the original suspension and 10-1 dilution. Although fermentations were noted in the higher dilutions, the frequency of the fermentation and the degree of the dilution were not found related. In the cases of the M-type variant derived from E, , the corresponding bacterial count was found to be the dilution of 10-2 of the preceding case, and the frequency of the fermentation was found much lower.
In view of these observations, it was presumed that the apparently peculiar phenomenon is strongly related to the pronounce effects by galactose, lactose etc. on the bacterial body M-type variant grown on E. or on GE.. When considered furthermore, although the phenomenon seems to be due to the fact that the number of viable organism in the colonies grown on E. or on G. E. is less than those in the colonies grown on ordinary agar, the phenomenon suggests the necessity of further invesgat ions in the qualitative difference supposes to be existing between these two cases since GP water was fermented by an extremely minute amount of the brown in the peptone water containing mixture of the sugars. In addition, it was known that the effect of galactose in this repect is very strong, but that lactose is not less strong in this repect. On the contrary, the effect of rafnose is extremely weak. However, the reason for the weakness of the effect of raf inose cannot be attributed to the amount of galactose contained in the component of raffinose. Therefore, the weakness of the effect of rafliinose despite the large content of galactose is considered to be related to the chemical binding modes of the components of galactose, glucose etc.
As to the process of the appearance of the galactose fermenting strain, report is scheduled to follow at a later date.