토양에서 분리한 절대호알카리성 Bacillus sp. SH-8과 중성에서 생육이 가능한 변이주 Bacillus sp. SH-8M을 중성 (pH 7.7) 및 알카리성 (pH 10.2) 환경하에서 생육시키면서 ΔpH의 변화와 세포외 Na^+이온의 농도를 검토하였다. 알카리성에서 ΔpH는 두 균주 모두 배양 10시간 후부터 70∼82mV 범위에 있었으며, 중성에서 Bacillus sp. SH-8은 배양 시간에 따라 ΔpH가 감소하여 12시간 후에는 약 23mv를 나타내었으나, Bacillus sp. SH-8M은 75∼83mv의 ΔpH 값을 나타내었다. 알카리성 환경하에서 배양시키면서 세포외 Na^+ 이온 농도를 측정한 결과, 두 균주 모두 배양 시간에 따라 세포외 Na^+ 이온 농도의 증감을 나타내었으며 최고 증감폭은 870∼900㎍/㎖이었다 그러나 Bacillus sp. SH-8M의 중성 환경하에서 배양시 Na^+ 이온의 이동은 알칼리성 환경에서 보다는 적었으나 NaCl을 첨가한 중성 환경하에서는 알카리성 환경에서의 Na^+이온 이동의 폭과 유사한 현상을 나타내었다.

To understand the differences in the physiological characteristics between neutrophile and alkalophile, an absolute alkalophilic Bacillus sp. SH-8 which was able to grow only at alkaline pH range up to pH 11.0 was isolated from the soil, and its mutant strain, SH-8M which was able to grow both at neutral and alkaline pH was obtained by UV mutagenesis. The changes of ΔpH and Na^+ ion concentration in the wild type and the mutant strain were then measured under various growth conditions. The ΔpH value of the two strains were calculated to be within the range of 70∼82㎷ in alkaline condition (pH 10.2). In neutral condition (pH 7.7) the ΔpH value of SH-8 strain was decreased to 23㎷ but that of SH-8M was maintained at the level of 62-83㎷. The circulation of Na^+ ions through cell membranes of the both strains at pH 10.2 and pH 7.7 was detected. When the two strains were cultured in the alkaline condition, high fluctuation in the external Na^+ ion concentration was observed to be 870∼900㎍/㎖, but when the mutant strain SH-8M was cultured in the neutral condition, the fluctuation was reduced and became to be increased to the same level in the alkaline condition by addition of NaCl to the medium. This may indicate that functional Na^+/H^+ antiporter and Na^+/solute symporter are present in the membrane of two strains.