XPORT ENTRAP: A droplet microfluidic platform for enhanced DNA transfer between microbial species

A significant hurdle for the widespread implementation and use of synthetic biology is the challenge of highly efficient introduction of DNA into microorganisms. This is especially a barrier for the utilization of non-model organisms and/or novel chassis species for a variety of applications, ranging from molecular biology to biotechnology and biomanufacturing applications. Common approaches to episomal and chromosomal gene editing, which employ techniques such as chemical competence and electroporation, are typically only amenable to a small subset of microbial species while leaving the vast majority of microorganisms in nature genetically inaccessible. To address this challenge, we have employed the previously described B. subtilis broad-host conjugation strain, XPORT, which was modularly designed for loading DNA cargo and conjugating such DNA into recalcitrant microbes. In this current work, we have leveraged and adapted the XPORT strain for use in a droplet microfluidic platform to enable increased efficiency of conjugation-based DNA transfer. The system named DNA ENTRAP (DNA ENhanced TRAnsfer Platform) utilizes cell-encapsulated water-in-oil emulsion droplets as pico-liter-volume bioreactors that allows controlled contacts between the donor and receiver cells within the emulsion bioreactor. This allowed enhanced XPORT-mediated genetic transfer over the current benchtop XPORT process, demonstrated using two different Bacillus subtilis strains (donor and receiver), as well as increased throughput (e.g., number of successfully conjugated cells) due to the automated assay steps inherent to microfluidic lab-on-a-chip systems. DNA ENTRAP paves the way for a streamlined automation of culturing and XPORT-mediated genetic transfer processes as well as future high-throughput cell engineering and screening applications.