Dynamic density shaping of photokinetic E. coli.
Dynamic density shaping of photokinetic E. coli.
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DOI：
10.7554/elife.36608
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发表时间：
2018-08-14
期刊：
影响因子：
7.7
通讯作者：
Di Leonardo R
中科院分区：
文献类型：
--
作者：
Frangipane G;Dell'Arciprete D;Petracchini S;Maggi C;Saglimbeni F;Bianchi S;Vizsnyiczai G;Bernardini ML;Di Leonardo R
许多运动微生物对环境光信号做出反应，产生各种运动反应，引导细胞获得更好的生存和生长条件。空间光调制器的使用可以帮助阐明光运动的机制，同时提供一种有效的策略来实现细胞浓度的空间和时间控制。在这里，我们证明了数以百万计的细菌经过基因改造，可以以光可控的速度平稳游动，可以使用数字光投影仪将其排列成复杂且可重新配置的密度模式。我们证明，自由游动的均匀细菌海洋可以在复杂的形状之间变形。我们对光响应中记忆产生的非局部效应进行建模，并展示如何通过反馈控制策略来减轻这些效应，从而实现灰度密度图像的详细再现。许多细菌可以响应环境信号而移动。这有助于引导它们获得更好的生长和生存条件。大肠杆菌是一种可以在液体中快速游动的细菌，利用每秒旋转多次的微小螺旋桨结构。这些“螺旋桨”由称为鞭毛马达的细胞马达提供动力，它类似于电动机，需要能源来驱动运动。变形视紫红质是一种最初从海洋中自由游动的微生物中分离出来的蛋白质，是帮助细菌移动的替代能源。这种蛋白质位于靠近细胞表面的位置，它的作用就像太阳能电池板一样，从光中捕获能量。在由变形视紫红质驱动的细胞中，环境中的光强度决定了它们的游泳速度：更亮的光意味着更快的运动，而更少的光意味着更慢的运动。变形视紫红质现在也是实验室中的有用工具。例如，通过基因工程改造细菌来产生蛋白视紫红质，提供了一种使用光源远程控制其运动的方法。众所周知，游泳细菌就像城市交通中的汽车一样，会在速度降低的区域积聚。通过利用变形视紫红质控制游泳速度，研究人员可以简单地通过投射不同模式的光来控制细菌的局部密度。为了研究影响这一现象的因素，Frangipane 等人。使用转基因大肠杆菌，它可以通过变形视紫红质对光做出反应，从而形成细胞层，然后将光图案投射到它们上面。结果表明，细菌对这些刺激的反应缓慢，这是限制它们形成的最终图案分辨率的主要因素。一个简单的反馈机制，将细胞形成的图案与所需的图像进行比较，并相应地更新投射光，就足以解决这个问题。这样，大肠杆菌层就可以变成原始图像近乎完美的副本。这项工作使我们能够比以往更精确地控制大量细菌的运动。这对于构建下一代微型设备非常有价值。例如，可以使细菌包围较大的物体，例如机器零件或药物载体，然后用作活的螺旋桨，将其运输到需要的地方。
Many motile microorganisms react to environmental light cues with a variety of motility responses guiding cells towards better conditions for survival and growth. The use of spatial light modulators could help to elucidate the mechanisms of photo-movements while, at the same time, providing an efficient strategy to achieve spatial and temporal control of cell concentration. Here we demonstrate that millions of bacteria, genetically modified to swim smoothly with a light controllable speed, can be arranged into complex and reconfigurable density patterns using a digital light projector. We show that a homogeneous sea of freely swimming bacteria can be made to morph between complex shapes. We model non-local effects arising from memory in light response and show how these can be mitigated by a feedback control strategy resulting in the detailed reproduction of grayscale density images. Many bacteria can move in response to environmental signals. This helps guide them towards better conditions for growth and survival. Escherichia coli is a bacterium that can swim quickly through liquid, using tiny propeller-like structures that rotate many times per second. These ‘propellers’ are powered by a cellular motor, called the flagellar motor, which similar to an electric motor, requires an energy source to drive movement. Proteorhodopsin, a protein originally isolated from free-swimming micro-organisms in the ocean, is an alternative energy source that helps bacteria move. The protein is located close to the surface of the cell, where it acts like a solar panel and captures energy from light. In cells powered by proteorhodopsin, the intensity of light from their environment determines their swimming speed: brighter light means faster movement, and less light, slower movement. Proteorhodopsin is now also a useful tool in the laboratory. For example, genetically engineering bacteria to produce proteorhodopsin provides a way to control their movement remotely, using a light source. Swimming bacteria, much like cars in city traffic, are known to accumulate in areas where their speed decreases. By controlling swimming speed with proteorhodopsin, researchers can manipulate the local density of bacteria simply by projecting different patterns of light. To study the factors influencing this phenomenon, Frangipane et al. used genetically modified E. coli that could respond to light via proteorhodopsin to make layers of cells that could then have light patterns projected onto them. The results showed that the bacteria responded slowly to these stimuli, which was the main factor limiting the resolution of the final pattern they formed. A simple feedback mechanism, which compared the pattern formed by the cells to the desired image and updated the projected light accordingly, was enough to solve this problem. This way, the layers of E.coli could be turned into a near-perfect copy of the original image. This work allows us to control the movement of large populations of bacteria more precisely than ever before. This could be extremely valuable for building the next generation of microscopic devices. For example, bacteria could be made to surround a larger object such as a machine part or a drug carrier, and then used as living propellers to transport it where it is needed.