Acetobacter aceti possesses a proton motive force-dependent efflux system for acetic acid
Acetobacter aceti possesses a proton motive force-dependent efflux system for acetic acid
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DOI：
10.1128/jb.187.13.4346-4352.2005
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发表时间：
2005-07-01
影响因子：
3.2
通讯作者：
Toyama, H
中科院分区：
文献类型：
--
作者：
Matsushita, K;Inoue, T;Toyama, H
醋酸菌是专性需氧菌，能够将乙醇、糖醇和糖氧化成相应的酸。其中醋酸杆菌（Acetobacter）和葡萄糖醋酸杆菌（Gluconacetobacter）具有非常高的乙醇氧化能力，导致大量乙酸在细胞外积累。由于这些细菌能够在高浓度乙酸的培养基中生长，因此它们必须具有特定的机制，例如外排泵，通过该机制它们可以抵抗乙酸的毒性作用。本研究采用完整的细胞和膜泡检测醋酸杆菌IFO 3283的外排泵。添加质子解耦剂和/或氰化物增加了完整细胞中乙酸/醋酸酯的积累，表明存在能量依赖的外排系统。为了证实这一点，我们用醋酸A. aceti IFO 3283制备了由右向外和由内向外的膜囊泡，并检测了乙酸/乙酸在囊泡中的积累情况。在添加呼吸底物后，醋酸/醋酸酯在右侧外囊泡中的积累量大大减少，而在内向外囊泡中的积累量则大大增加。在两种类型的膜泡中观察到的这些呼吸依赖现象都对质子解耦剂敏感。内外膜囊泡对乙酸/乙酸的摄取不依赖于ATP，而依赖于质子动力。此外，醋酸的摄取被证明是相当特定的，并且与pH有关，因为在较低的pH下观察到较高的摄取。因此，a.b乙酰IFO 3283具有依赖于质子动力的醋酸外排泵。
Acetic acid bacteria are obligate aerobes able to oxidize ethanol, sugar alcohols, and sugars into their corresponding acids. Among them, Acetobacter and Gluconacetobacter species have very high ethanol oxidation capacity, leading to accumulation of vast amounts of acetic acid outside the cell. Since these bacteria are able to grow in media with high concentrations of acetic acid, they must possess a specific mechanism such as an efflux pump by which they can resist the toxic effects of acetic acid. In this study, the efflux pump of Acetobacter aceti IFO 3283 was examined using intact cells and membrane vesicles. The accumulation of acetic acid/acetate in intact cells was increased by the addition of a proton uncoupler and/or cyanide, suggesting the presence of an energy-dependent efflux system. To confirm this, right-side-out and inside-out membrane vesicles were prepared from A. aceti IFO 3283, and the accumulation of acetic acid/acetate in the vesicles was examined. Upon the addition of a respiratory substrate, the accumulation of acetic acid/acetate in the right-side-out vesicles was largely decreased, while its accumulation was very much increased in the inside-out vesicles. These respiration-dependent phenomena observed in both types of membrane vesicles were all sensitive to a proton uncoupler. Acetic acid/acetate uptake in the inside-out membrane vesicles was dependent not on ATP but on the proton motive force. Furthermore, uptake was shown to be rather specific for acetic acid and to be pH dependent, because higher uptake was observed at lower pH. Thus, A. aceti IFO 3283 possesses a proton motive force-dependent efflux pump for acetic acid.