Microfluidic Technologies for Continuous Culture and Genetic Circuit Characterization

In this thesis, I have used microfluidics--the science and technology of systems that manipulate small amounts of fluids (10-9 to 10-18 liters) in microsized channels--to invent and implement a miniaturized continuous culture device or microchemostat. It relies on a novel in silicone sterilization approach to circumventing biofilm formation. The microchemostat system has inbuilt automation, which allows it to run, unattended, indefinitely (for up to months at a time). With a working volume of ~10 nL, the microchemostat is capable of culturing extremely small populations of bacteria (100 to ~104 cells vs ~109 in macroscale cultures). The microsized population reduces the number of cell-division events per unit time and hence slows down microbial evolution. This aspect facilitates long-term monitoring of the behavior of genetically engineered microbes while preserving their genetic homogeneity. Unlike its conventional continuous-culture counterparts, the microchemostat allows simultaneous operation of fourteen (or more) independent microreactors which enjoy ultralow consumption of medium and biological reagents, allowing high-throughput research at low cost. It also facilitates automated, noninvasive monitoring of bacterial behavior in terms of bacterial count, cell morphology as well as single-cell resolved gene-expression dynamics reported by fluorescence or luminescence. The unprecedented temporal and single cell resolution readings allow the microchemostat to capture dynamics such as delicate oscillations that have eluded detection in conventional settings. Thanks to its unique capability for long-term culturing and suppression of microbial evolution, the microchemostat promises to become integrated as an ingredient of a multicomponent monolithic entity in future applications. The microchemostat would mainly be responsible for in silicone production and supply of genetically homogeneous bacteria for use in various capacities.