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

• Published in: Lab on a chip 2015-01, Vol.15 (3), p.889-899
• Main Authors: Jeong, Heon-Ho, Jin, Si Hyung, Lee, Byung Jin, Kim, Taesung, Lee, Chang-Soo
• Format: Article
• Language: English
• Subjects: Arrays; Bacteria; Droplets; Escherichia coli - growth & development; Escherichia coli - isolation & purification; Escherichia coli - metabolism; Hydrodynamics; Microfluidic Analytical Techniques - instrumentation; Microfluidics; Microorganisms; Particle Size; Partnerships; Population density; Quorum Sensing; Receivers; Surface Properties
• ISSN: 1473-0197; 1473-0189
• DOI: 10.1039/c4lc01097c

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.