title: Relationship between rates of respiratory proton extrusion and ATP synthesis in obligately alkaliphilic Bacillus clarkii DSM 8720(T).
abstract: To elucidate the energy production mechanism of alkaliphiles, the relationship between the rate of proton extrusion via the respiratory chain and the corresponding ATP synthesis rate was examined in obligately alkaliphilic Bacillus clarkii DSM 8720(T) and neutralophilic Bacillus subtilis IAM 1026. The oxygen consumption rate of B. subtilis IAM 1026 cells at pH 7 was approximately 2.5 times higher than that of B. clarkii DSM 8720(T) cells at pH 10. The H⁺/O ratio of B. clarkii DSM 8720(T) cells was approximately 1.8 times higher than that of B. subtilis IAM 1026 cells. On the basis of oxygen consumption rate and H⁺/O ratio, the rate of proton translocation via the respiratory chain in B. subtilis IAM 1026 is expected to be approximately 1.4 times higher than that in B. clarkii DSM 8720(T). Conversely, the rate of ATP synthesis in B. clarkii DSM 8720(T) at pH 10 was approximately 7.5 times higher than that in B. subtilis IAM 1026 at pH 7. It can be predicted that the difference in rate of ATP synthesis is due to the effect of transmembrane electrical potential (Δψ) on protons translocated via the respiratory chain. The Δψ values of B. clarkii DSM 8720(T) and B. subtilis IAM 1026 were estimated as -192 mV (pH 10) and -122 mV (pH 7), respectively. It is considered that the discrepancy between the rates of proton translocation and ATP synthesis between the strains used in this study is due to the difference in ATP production efficiency per translocated proton between the two strains caused by the difference in Δψ.
authors.affiliation: Department of Bioscience and Technology, School of Biological Science and Engineering, Tokai University, Minaminosawa, Minami-ku, Sapporo, Hokkaido 005-8601, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Hirabayashi
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Goto
authors.forename: Hajime
authors.initials: H
authors.lastname: Morimoto
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yoshimune
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Matsuyama
authors.forename: Isao
authors.initials: I
authors.lastname: Yumoto
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D001407:Bacillus / Q000502:physiology*; D004579:Electron Transport / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D018892:Proton-Motive Force / Q000502:physiology*; D011522:Protons
chemical_list: D011522:Protons; D000255:Adenosine Triphosphate