Helical and rod-shaped bacteria swim in helical trajectories with little additional propulsion from helical shape.
Helical and rod-shaped bacteria swim in helical trajectories with little additional propulsion from helical shape.
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螺旋形和棒状细菌在螺旋轨迹中游泳，几乎没有螺旋形的推进。
DOI：
10.1126/sciadv.1601661
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发表时间：
2016-11
期刊：
影响因子：
13.6
通讯作者：
Bansil R
中科院分区：
文献类型：
--
作者：
Constantino MA;Jabbarzadeh M;Fu HC;Bansil R
螺旋状细菌，如胃病原体H。pylori，游泳只比它们的同基因杆状突变体快15%左右。人们经常假设，鞭毛细菌的螺旋体形状可能在游泳能力方面产生一些优势。特别是，螺旋形的病原体幽门螺杆菌经常被声称像开瓶器一样在其恶劣的胃栖息地游泳，但没有直接证实或量化这种说法。使用快速的时间分辨率和高放大率的二维（2D）相衬显微镜，同时图像和跟踪单个细菌的细菌肉汤以及粘蛋白的解决方案，我们表明，无论是螺旋形和棒状H。pylori在游动时旋转，形成螺旋形轨迹。细胞形状分析使我们能够确定形状以及旋转和平移速度的向前和向后的运动，从而推断鞭毛运动学。使用正则化Stokeslets的方法，我们直接比较观察到的速度和轨迹的数值计算的螺旋和杆状细菌粘蛋白和肉汤，以验证数值模型。尽管实验观察仅限于选定的情况，但该模型允许量化主体螺旋度、长度和直径的影响。我们发现，由于相对缓慢的身体旋转速率，螺旋形状，使最多15%的贡献，推进推力。体型对游泳速度的影响主要取决于移动细胞体所需的平移阻力的变化。由于螺旋细胞是由细胞体产生的推进力的最强候选者之一，我们的研究结果意味着，一般来说，鞭毛细菌的游泳速度只能通过身体推进力增加一点点。
Helical bacteria, like the stomach pathogen H. pylori, swim only about 15% faster than their isogenic rod-shaped mutants. It has frequently been hypothesized that the helical body shapes of flagellated bacteria may yield some advantage in swimming ability. In particular, the helical-shaped pathogen Helicobacter pylori is often claimed to swim like a corkscrew through its harsh gastric habitat, but there has been no direct confirmation or quantification of such claims. Using fast time-resolution and high-magnification two-dimensional (2D) phase-contrast microscopy to simultaneously image and track individual bacteria in bacterial broth as well as mucin solutions, we show that both helical and rod-shaped H. pylori rotated as they swam, producing a helical trajectory. Cell shape analysis enabled us to determine shape as well as the rotational and translational speed for both forward and reverse motions, thereby inferring flagellar kinematics. Using the method of regularized Stokeslets, we directly compare observed speeds and trajectories to numerical calculations for both helical and rod-shaped bacteria in mucin and broth to validate the numerical model. Although experimental observations are limited to select cases, the model allows quantification of the effects of body helicity, length, and diameter. We find that due to relatively slow body rotation rates, the helical shape makes at most a 15% contribution to propulsive thrust. The effect of body shape on swimming speeds is instead dominated by variations in translational drag required to move the cell body. Because helical cells are one of the strongest candidates for propulsion arising from the cell body, our results imply that quite generally, swimming speeds of flagellated bacteria can only be increased a little by body propulsion.