<i>In Vivo</i> Gene Expression Dynamics of Tumor-Targeted Bacteria

Abstract

The engineering of bacteria to controllably deliver therapeutics is an attractive application for synthetic biology. While most synthetic gene networks have been explored within microbes, there is a need for further characterization of <i>in vivo</i> circuit behavior in the context of applications where the host microbes are actively being investigated for efficacy and safety, such as tumor drug delivery. One major hurdle is that culture-based selective pressures are absent <i>in vivo</i>, leading to strain-dependent instability of plasmid-based networks over time. Here, we experimentally characterize the dynamics of <i>in vivo</i> plasmid instability using attenuated strains of <i>S. typhimurium</i> and real-time monitoring of luminescent reporters. Computational modeling described the effects of growth rate and dosage on live-imaging signals generated by internal bacterial populations. This understanding will allow us to harness the transient nature of plasmid-based networks to create tunable temporal release profiles that reduce dosage requirements and increase the safety of bacterial therapies