Ilkanaiv Bella, Kearns Daniel B, Ariel Gil, Be'er Avraham
Zuckerberg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Midreshet Ben-Gurion, Israel.
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Phys Rev Lett. 2017 Apr 14;118(15):158002. doi: 10.1103/PhysRevLett.118.158002. Epub 2017 Apr 12.
Swarming bacteria collectively migrate on surfaces using flagella, forming dynamic whirls and jets that consist of millions of individuals. Because some swarming bacteria elongate prior to actual motion, cell aspect ratio may play a significant role in the collective dynamics. Extensive research on self-propelled rodlike particles confirms that elongation promotes alignment, strongly affecting the dynamics. Here, we study experimentally the collective dynamics of variants of swarming Bacillus subtilis that differ in length. We show that the swarming statistics depends on the aspect ratio in a critical, fundamental fashion not predicted by theory. The fastest motion was obtained for the wild-type and variants that are similar in length. However, shorter and longer cells exhibit anomalous, non-Gaussian statistics and nonexponential decay of the autocorrelation function, indicating lower collective motility. These results suggest that the robust mechanisms to maintain aspect ratios may be important for efficient swarming motility. Wild-type cells are optimal in this sense.
群体游动的细菌利用鞭毛在表面集体迁移，形成由数百万个个体组成的动态漩涡和喷射流。由于一些群体游动细菌在实际运动前会伸长，细胞的长宽比可能在集体动力学中发挥重要作用。对自驱动棒状粒子的广泛研究证实，伸长促进排列，对动力学有强烈影响。在这里，我们通过实验研究了不同长度的群体游动枯草芽孢杆菌变体的集体动力学。我们表明，群体游动统计数据以一种理论未预测到的关键、基本方式依赖于长宽比。野生型和长度相似的变体获得了最快的运动速度。然而，较短和较长的细胞表现出异常的、非高斯统计以及自相关函数的非指数衰减，表明集体运动性较低。这些结果表明，维持长宽比的稳健机制对于高效的群体游动运动性可能很重要。从这个意义上说，野生型细胞是最优的。
