Active living emulsions driven by bacteria

第1部分：非技术概述：游动的细菌是一种新型“活性”乳剂的吸引人的成分：由细菌驱动其运动的液滴的悬浮液。这种活性乳剂代表着生物材料的潜在变革性进步，因为它们将生命系统的理想特性--如极端机械性能、复杂的催化能力和自我修复--融入到易于打印或成型的工程材料中。在乳状液中获得这些特性是具有挑战性的，因为目前还不知道如何根据细菌的运动来预测乳状液的整体流动特性。该项目将开发必要的工具，通过设计细菌的运动性和粘附性来对活性乳剂的机械性能进行编程，并通过了解外部“游泳者”的运动如何转化为乳状液的集体液滴运动和“流动性”来解决一个关键的知识缺口。该项目的成果有望推动先进材料加工和3D打印应用的原料设计。PI和学生实习生团队将通过当地会议向休斯顿的生物医学和材料社区传播结果，并为德克萨斯州的初级研究人员建立研讨会系列。他们还将通过德克萨斯软物质会议发起一个多语言的公共推广活动，并为他们通过休斯顿大学为K-12学生和休斯顿能源节上的公众正在进行的推广计划开发新的活动。PART 2：技术概述：该项目的目标是发展编程活的活性乳液所需的基本理解，在这些乳液中，悬浮液滴的定向旋转是由细菌的运动驱动的。为了测试细菌驱动的乳液滴之间的集体相互作用可以用来修改和控制乳液的宏观机械性能的假设，PI将整合软物质物理(CONRAD)和合成生物学(CIRINO)方面的互补专业知识，以满足两个特定目标：(1)通过细菌界面相互作用控制液滴的流动性，以及(2)将活乳液的宏观流变学与微观集体液滴的运动联系起来。由PI以及本科生和研究生实习生组成的团队将为非模式生物海洋杆菌氢碳棒杆菌SP1开发基因工具，并构建表面特征表达可调的转基因细菌。由工程细菌驱动的液滴运动测量将用于测试旋转速度和随机平移运动的模型。该团队将量化旋转液滴之间的成对相互作用，测量浓缩乳状液中的旋转速度和相关长度，并将与液滴集体运动相关的长度尺度与活性乳状液的整体机械性能联系起来。这些研究将对细菌的微观活动与宏观乳液机制之间的关系产生新的见解，这将为活性乳液作为一种新的生物材料的开发铺平道路。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARY:Swimming bacteria are appealing components in a novel class of “active” emulsions: suspensions of droplets whose motion is driven by bacteria. Such living active emulsions represent a potentially transformative advance in biomaterials, as they incorporate desirable properties of living systems – such as extreme mechanical properties, complex catalytic capabilities, and self-healing – into engineered materials that can be readily printed or shaped. Attaining these properties in emulsions is challenging because it is not currently known how to predict the bulk flow properties of emulsions from the motion of bacteria. This project will develop the tools needed to program the mechanical properties of living active emulsions by engineering the motility and adhesiveness of bacteria and address a critical knowledge gap by providing understanding of how the motion of external “swimmers” is transduced into collective droplet motion and “flowability” of emulsions. The results from this project are expected to advance the design of feedstocks for state-of-the-art materials processing and 3-D printing applications. The team of PIs and student trainees will disseminate results to Houston’s biomedical and materials communities through local meetings and establish a seminar series for junior Texas researchers. They will also initiate a multilingual public outreach event through the Texas Soft Matter Meeting and develop new activities for their ongoing outreach programs for K - 12 students through the University of Houston and for the public at the Houston Energy Festival.PART 2: TECHNICAL SUMMARY:The objective of this project is to develop the fundamental understanding needed to program living active emulsions in which directional rotation of suspended droplets is driven by bacterial motility. To test the hypothesis that collective interactions between bacteria-driven emulsion droplets can be used to modify and control the macroscopic mechanical properties of emulsions, the PIs will integrate complementary expertise in soft-matter physics (Conrad) and synthetic biology (Cirino) to address two specific aims: (1) control droplet mobility via bacterial interfacial interactions, and (2) link macroscopic rheology of living emulsions to microscopic collective droplet motion. The team of PIs and undergraduate and graduate student trainees will advance genetic tools for the non-model organism Marinobacter hydrocarbonoclasticus SP1 and construct genetically modified bacteria with tunable expression of surface features. Measurements of droplet motion driven by engineered bacteria will be used to test models for the rotation rate and for stochastic translational motion. The team will quantify pairwise interactions between rotating droplets, measure rotation speed and correlation length in concentrated emulsions, and relate length scales associated with collective droplet motion to the bulk mechanical properties of active emulsions. These studies will generate new insight into how the microscopic activity of bacteria is related to the macroscopic emulsion mechanics, which will pave the way for the development of living active emulsions as a new class of biomaterials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.