Active living emulsions driven by bacteria

University Of Houston, Houston TX

Investigators

Abstract

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.