Force generation by groups of migrating bacteria
Force generation by groups of migrating bacteria
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DOI：
10.1073/pnas.1621469114
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发表时间：
2017-01
期刊：
影响因子：
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通讯作者：
B. Sabass;Matthias D. Koch;Guannan Liu;H. Stone;J. Shaevitz
中科院分区：
文献类型：
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作者：
B. Sabass;Matthias D. Koch;Guannan Liu;H. Stone;J. Shaevitz
重要的是，细菌的迁移、聚集，甚至宿主感染都依赖于机械力的产生。尽管它们在生物医学上很重要，但在迁移过程中还没有测量到细菌和表面之间的力。我们提出了第一个研究细菌细胞-底物牵引力以黄色粘球菌为模式生物。黄曲霉表现出两种常见的运动机制，即抽动和滑动。我们发现，这些机制导致在运动过程中作为个人或群体的不同的牵引力模式。抽动导致局部的、不协调的牵引力，群体滑行允许集体出现定向牵引力。当细胞成群移动时，单个细胞的抽动或滑动产生的力会显著放大。从细菌的集落形成到多细胞生物体的伤口愈合和胚胎发育，活细胞群必须经常集体移动。虽然已经有相当多的研究探索了真核细胞在迁移过程中如何产生力的生物物理机制，但对细菌的研究很少，特别是关于细菌如何在集体运动中产生和协调力的问题。这个问题在这里用牵引力显微镜来解决。我们研究了黄色粘球菌的两种不同的运动机制，即抽动和滑动。对于由IV型毛发收缩提供动力的抽动，我们发现单个细胞在小的热点区域施加局部牵引力，作用力约为50pN。抽动的细菌群也会产生牵引力热点，但其作用力在100pN左右，在1.5分钟的时间尺度上迅速波动。滑动是第二种运动机制，是由底物粘连的横向运输驱动的。当细胞被分离时，滑动产生的平均牵引力较低，约为1pa。然而，牵引力在群体中被放大了大约五倍。滑动细胞的前移突起平均向运动方向推进。综上所述，这些结果表明，在抽动和滑行过程中产生的力具有互补性，并且当细胞成群时，这两种力的值更高。
Significance Bacterial migration, aggregation, and even host infection depend on the generation of mechanical force. Despite their biomedical importance, forces between bacteria and surfaces have not yet been measured during migration. We present a first study of bacterial cell–substrate traction using Myxococcus xanthus as a model organism. M. xanthus exhibits two common mechanisms of motility, namely, twitching and gliding. We find that these mechanisms lead to distinct patterns of traction during motion as an individual or in groups. Twitching leads to local, uncoordinated traction, and gliding in groups allows for collective emergence of directional traction. The forces produced by twitching or gliding of individual cells are significantly amplified when cells move in groups. From colony formation in bacteria to wound healing and embryonic development in multicellular organisms, groups of living cells must often move collectively. Although considerable study has probed the biophysical mechanisms of how eukaryotic cells generate forces during migration, little such study has been devoted to bacteria, in particular with regard to the question of how bacteria generate and coordinate forces during collective motion. This question is addressed here using traction force microscopy. We study two distinct motility mechanisms of Myxococcus xanthus, namely, twitching and gliding. For twitching, powered by type-IV pilus retraction, we find that individual cells exert local traction in small hotspots with forces on the order of 50 pN. Twitching bacterial groups also produce traction hotspots, but with forces around 100 pN that fluctuate rapidly on timescales of <1.5 min. Gliding, the second motility mechanism, is driven by lateral transport of substrate adhesions. When cells are isolated, gliding produces low average traction on the order of 1 Pa. However, traction is amplified approximately fivefold in groups. Advancing protrusions of gliding cells push, on average, in the direction of motion. Together, these results show that the forces generated during twitching and gliding have complementary characters, and both forces have higher values when cells are in groups.