Direct observation of rotation and steps of the archaellum in the swimming halophilic archaeon Halobacterium salinarum
Direct observation of rotation and steps of the archaellum in the swimming halophilic archaeon Halobacterium salinarum
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DOI：
10.1038/nmicrobiol.2016.148
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发表时间：
2016-11-01
影响因子：
28.3
通讯作者：
Nishizaka, Takayuki
中科院分区：
文献类型：
--
作者：
Kinosita, Yoshiaki;Uchida, Nariya;Nishizaka, Takayuki
运动的古细菌利用旋转的丝状体（古菌）游动，古菌是一种表面附属物，在结构上类似于细菌的鞭毛，但与细菌IV型皮利同源。关于古细菌产生运动的机制知之甚少。为了深入了解这一机制，我们在模式生物盐生盐杆菌中表征了古菌的功能。量子点的三维跟踪使古生菌的左旋螺旋详细可视化。一种先进的分析方法结合全内反射荧光显微镜，称为交叉kymography，被开发出来，并揭示了右手螺旋结构的古菌与旋转速度为23 +/- 5赫兹。使用这些结构和动力学参数，我们计算再现的游泳和进动运动的流体动力学模型和估计的古菌电机扭矩为50 pN nm。最后，在拴系细胞测定中，我们观察到在旋转期间以类似于36度或60度的间隔间歇性暂停，我们推测这可能是消耗单个三磷酸腺苷分子的单一步骤，其在水解时提供80 pN nm的化学能。根据每转10或6个三磷酸腺苷的能量输入的估计，马达的效率被计算为类似于6- 10%。
Motile archaea swim using a rotary filament, the archaellum, a surface appendage that resembles bacterial flagella structurally, but is homologous to bacterial type IV pili. Little is known about the mechanism by which archaella produce motility. To gain insights into this mechanism, we characterized archaellar function in the model organism Halobacterium salinarum. Three-dimensional tracking of quantum dots enabled visualization of the left-handed corkscrewing of archaea in detail. An advanced analysis method combined with total internal reflection fluorescence microscopy, termed cross-kymography, was developed and revealed a right-handed helical structure of archaella with a rotation speed of 23 +/- 5 Hz. Using these structural and kinetic parameters, we computationally reproduced the swimming and precession motion with a hydrodynamic model and estimated the archaellar motor torque to be 50 pN nm. Finally, in a tethered-cell assay, we observed intermittent pauses during rotation with similar to 36 degrees or 60 degrees intervals, which we speculate may be a unitary step consuming a single adenosine triphosphate molecule, which supplies chemical energy of 80 pN nm when hydrolysed. From an estimate of the energy input as ten or six adenosine triphosphates per revolution, the efficiency of the motor is calculated to be similar to 6-10%.