(293f) Invited Speaker: Drop Stabilization on a Chip (DropSOAC): Stabilizing Microfluidic Drops for Time-Lapse Quantification of Single-Cell Bacterial Physiology

The physiological heterogeneity of cells within a microbial population imparts resilience to stresses such as antimicrobial treatments and nutrient limitation. Cellular heterogeneity can allow for a subpopulation of cells to survive such stresses and regenerate the community. Microfluidic approaches provide a means to study microbial physiology and bacterial heterogeneity at the single cell level, improving our ability to isolate and examine these subpopulations. Specifically, drop-based microfluidics provides a high-throughput approach to examine individual cell physiology within bacterial populations. Here, we present a simple and high-throughput method, called DropSOAC (Drop Stabilization On A Chip), that allows for imaging of individual bacterial cells within an array of microscale drops over time. The drops are less than 20 µm in diameter and remain stable as a packed monolayer under time-lapse imaging for over 20 hours. Approximately one hundred thousand individual drops can be incubated within a DropSOAC microfluidic device. Using DropSOAC, we demonstrate that growth rate and lag time heterogeneity of hundreds of individual bacterial cells can be determined starting from single isolated cells. We characterize growth of Pseudomonas aeruginosa and its Δhpf mutant derivative during resuscitation and growth following starvation. The results show that the DropSOAC method provides a high-throughput approach toward studies of microbial physiology at the single cell level, and can be used to characterize physiological differences of cells from within a larger population. This work provides a deeper understanding of drop emulsion stability within a porous PDMS microfluidic device and will have future impact in studies of the physiological heterogeneity of single cells within other microbial populations.