Microfluidic static droplet array for analyzing microbial communication on a population gradient

Abstract

Quorum sensing (QS) is a type of cell-cell communication using signal molecules that are released and detected by cells, which respond to changes in their population density. A few studies explain that QS may operate in a density-dependent manner; however, due to experimental challenges, this fundamental hypothesis has never been investigated. Here, we present a microfluidic static droplet array (SDA) that combines a droplet generator with hydrodynamic traps to independently generate a bacterial population gradient into a parallel series of droplets under complete chemical and physical isolation. The SDA independently manipulates both a chemical concentration gradient and a bacterial population density. In addition, the bacterial population gradient in the SDA can be tuned by a simple change in the number of sample plug loading. Finally, the method allows the direct analysis of complicated biological events in an addressable droplet to enable the characterization of bacterial communication in response to the ratio of two microbial populations, including two genetically engineered QS circuits, such as the signal sender for acyl-homoserine lactone (AHL) production and the signal receiver bacteria for green fluorescent protein (GFP) expression induced by AHL. For the first time, we found that the population ratio of the signal sender and receiver indicates a significant and potentially interesting partnership between microbial communities. Therefore, we envision that this simple SDA could be a useful platform in various research fields, including analytical chemistry, combinatorial chemistry, synthetic biology, microbiology, and molecular biology.

Microfluidic Studies of Biofilm Formation in Dynamic Environments

“…In the work of Kim and coworkers (25), the advantage of microfluidics over classic flow cells also included the possibility of flexibly fabricating side grooves in which QS was studied, which would be very difficult with classic approaches. In addition, the ability to control the density of bacteria in microfluidic devices down to a few cells has given further insights into QS processes in small populations and confined environments (51,52).…”

Synthetic Microbial Ecology: Engineering Habitats for Modular Consortia

“…For the microfluidic platform one could envision using the popular microfabrication technique of soft lithography and the polymer PDMS (Kim et al, 2008; Frimat et al, 2011; Hong S. et al, 2012; Hong S. H. et al, 2012; Leung et al, 2012; Jeong et al, 2015; Luo et al, 2015; Mohan et al, 2015). Besides being a quick and inexpensive method, soft lithography would allow to easily construct the reservoirs in which the cells would grow, the potentially complex network of channels connecting those compartments and pattern their surface should this be needed (Duffy et al, 1998; Anderson et al, 2000; McDonald et al, 2000; Whitesides et al, 2001; McDonald and Whitesides, 2002).…”

Efficient and reliable screening of anti-obesity agents on a micro-cell pattern chip

“…Polydimethylsiloxane (PDMS) based microfluidic chips are frequently used for cell observations because they have many advantages such as non‐toxicity, a short‐term reaction, and low reagent consumption. A number of researchers have used microfluidic systems for new drug developments and for observing cell proliferation . However, these methods have limitations, such as labor‐intensive production, hard fabrication of microfluidic chips and difficult operation, and they seriously limit nutrient and oxygen uptake.…”