Real-time imaging of fluorescent flagellar filaments of Rhizobium lupini H13-3:: flagellar rotation and pH-induced polymorphic transitions
Real-time imaging of fluorescent flagellar filaments of Rhizobium lupini H13-3:: flagellar rotation and pH-induced polymorphic transitions
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DOI：
10.1128/jb.184.21.5979-5986.2002
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发表时间：
2002-11-01
影响因子：
3.2
通讯作者：
Scharf, B
中科院分区：
文献类型：
--
作者：
Scharf, B
土壤细菌羽扇豆根瘤菌H13-3具有复杂的右手鞭毛细丝，表面有不寻常的脊状凹槽。顺时针（CW）旋转推动细胞向前，而路线变化（翻滚）是由细丝速度的变化而不是更常见的旋转方向的变化引起的。鉴于这些新颖性，荧光标记被用来分析单个鞭毛丝在游泳和翻滚过程中的行为，从而导致R.卢皮尼。此外，鞭毛丝螺旋构象的变化，这还没有被证明是复杂的长丝进行了研究。在全速顺时针旋转过程中，鞭毛丝形成一个推进束，推动细胞沿着直线运动。翻滚是由单个鞭毛的异步减速和停止引起的，导致推进束的分离。R.羽扇豆翻滚不像其它生物体包括肠细菌中的翻滚那样伴随螺旋构象变化。然而，当实验改变pH时，观察到四种不同的多晶型形式。在生理pH值为7时，正常鞭毛螺旋的特征在于螺距角为30度，螺距为1.36 μ m，螺旋直径为0.50 μ m。随着pH值从9增加到11，螺旋从正常转变为半油状，再转变为直螺旋。随着pH值从5降低到3，螺旋由正常变为卷曲再变为直。在高粘度下也观察到瞬时构象变化，表明R。羽扇豆鞭毛丝可以通过呈现流体动力学有利的构象来适应粘性环境（土壤）中的高负荷。
The soil bacterium Rhizobium lupini H13-3 has complex right-handed flagellar filaments with unusual ridged, grooved surfaces. Clockwise (CW) rotation propels the cells forward, and course changes (tumbling) result from changes in filament speed instead of the more common change in direction of rotation. In view of these novelties, fluorescence labeling was used to analyze the behavior of single flagellar filaments during swimming and tumbling, leading to a model for directional changes in R. lupini. Also, flagellar filaments were investigated for helical conformational changes, which have not been previously shown for complex filaments. During full-speed CW rotation, the flagellar filaments form a propulsive bundle that pushes the cell on a straight path. Tumbling is caused by asynchronous deceleration and stops of individual filaments, resulting in dissociation of the propulsive bundle. R. lupini tumbles were not accompanied by helical conformational changes as are tumbles in other organisms including enteric bacteria. However, when pH was experimentally changed, four different polymorphic forms were observed. At a physiological pH of 7, normal flagellar helices were characterized by a pitch angle of 30degrees, a pitch of 1.36 mum, and a helical diameter of 0.50 mum. As pH increased from 9 to 11, the helices transformed from normal to semicoiled to straight. As pH decreased from 5 to 3, the helices transformed from normal to curly to straight. Transient conformational changes were also noted at high viscosity, suggesting that the R. lupini flagellar filament may adapt to high loads in viscous environments (soil) by assuming hydrodynamically favorable conformations.