Goto Toshitaka, Hirabayashi Toshinao, Morimoto Hajime, Yamazaki Koji, Inoue Norio, Matsuyama Hidetoshi, Yumoto Isao
Graduate School of Agriculture, Hokkaido University, Kita-ku, Sapporo, Hokkaido, 060-8589, Japan.
Bioproduction Research Insitute, National Institute of Advanced Science and Technology, 2-17-2-1, Tsukisamu-Higashi, Toyohira-ku, Sapporo, Hokkaido, 062-8517, Japan.
J Bioenerg Biomembr. 2016 Feb;48(1):87-96. doi: 10.1007/s10863-015-9641-9. Epub 2016 Jan 9.
To elucidate the energy production mechanism of alkaliphiles, the relationship between the H(+) extrusion rate by the respiratory chain and the corresponding ATP synthesis rate was determined in the facultative alkaliphile Bacillus cohnii YN-2000 and compared with those in the obligate alkaliphile Bacillus clarkii DSM 8720(T) and the neutralophile Bacillus subtilis IAM 1026. Under high aeration condition, much higher ATP synthesis rates and larger Δψ in the alkaliphilic Bacillus spp. grown at pH 10 than those in the neutralophilic B. subtilis grown at pH 7 were observed. This high ATP productivity could be attributed to the larger Δψ in alkaliphiles than in B. subtilis because the H(+) extrusion rate in alkaliphiles cannot account for the high ATP productivity. However, the large Δψ in the alkaliphiles could not be explained only by the H(+) translocation rate in the respiratory chain in alkaliphiles. There is a possibility that the Donnan effect across the membrane has the potential to contribute to the large Δψ. To estimate the contribution of the Donnan effect to the large Δψ in alkaliphilic Bacillus spp. grown at pH 10, intracellular negative ion capacity was examined. The intracellular negative ion capacities in alkaliphiles grown at pH 10 under high aeration condition corresponding to their intracellular pH (pH 8.1) were much higher than those in alkaliphiles grown under low aeration condition. A proportional relationship is revealed between the negative ion capacity and Δψ in alkaliphiles grown under different aeration conditions. This relationship strongly suggests that the intracellular negative ion capacity contributes to the formation of Δψ through the Donnan effect in alkaliphilic Bacillus spp. grown at pH 10.
为阐明嗜碱菌的能量产生机制，测定了兼性嗜碱菌科恩氏芽孢杆菌YN - 2000呼吸链的H⁺外排速率与相应的ATP合成速率之间的关系，并与专性嗜碱菌克拉克氏芽孢杆菌DSM 8720(T)和嗜中性枯草芽孢杆菌IAM 1026进行了比较。在高通气条件下，观察到在pH 10生长的嗜碱芽孢杆菌属中ATP合成速率更高，Δψ更大，而在pH 7生长的嗜中性枯草芽孢杆菌中则不然。这种高ATP生产力可能归因于嗜碱菌中的Δψ比枯草芽孢杆菌中的更大，因为嗜碱菌中的H⁺外排速率无法解释高ATP生产力。然而，嗜碱菌中较大的Δψ不能仅用嗜碱菌呼吸链中的H⁺转运速率来解释。膜两侧的唐南效应有可能对较大的Δψ有贡献。为估计唐南效应在pH 10生长的嗜碱芽孢杆菌属中对较大Δψ的贡献，检测了细胞内负离子容量。在高通气条件下于pH 10生长的嗜碱菌，对应其细胞内pH（pH 8.1）时，其细胞内负离子容量远高于在低通气条件下生长的嗜碱菌。在不同通气条件下生长的嗜碱菌中，揭示了负离子容量与Δψ之间的比例关系。这种关系强烈表明，在pH 10生长的嗜碱芽孢杆菌属中，细胞内负离子容量通过唐南效应有助于Δψ的形成。
