UC San Diego

A recent application for synthetic biological gene circuits has been in the realm of cancer diagnostics and therapeutics. Improvement and characterization of these circuits was conducted using three different methods. Firstly, using the synchronized lysis circuit (SLC), delivers cancer therapeutics in waves following oscillating lysis event, the spatiotemporal growth studied in motile bacteria[1,2]. The resulting patterns showed that the SLC strain was rendered immotile due to the stress of the circuit while the wild type showed chemotactic behavior, avoiding the SLC colony. It was discovered that bacteria enter a state of stress caused by overflow metabolism due to high glucose concentrations, resulting in lowered cAMP levels and loss of flagellar development and forcing fimbriae-based movement. This combination of wild type fimbriae motility with high glucose levels and non-motility of SLC strains was used to further observe dual-strain motility which creates flower shaped patterns. Additionally, improvements were made to a biosensor, which utilized horizontal gene transfer (HGT) to sense genetic material indicating presence of colorectal cancer (CRC) tumors[3]. Replacement of the tetracycline repression mechanism with a lacI based repression system was attempted. Further stability improvements were made in the sensor by deleting a prophage sequence and several insertion sequence copies, which increased sensitivity to tumor DNA. Furthermore, bacteria evolved using adaptive laboratory evolution (ALE) were characterized for growth and circuit behavior non-traditional media. Lastly, an inducible GFP lysis circuit was developed to better compare the lysis response between two strains of E. coli, MG1655 and Nissle 1917.