A discovery platform for identification of host-induced bacterial biosensors from diverse sources.

Synthetic biology approaches such as whole-cell biosensing and 'sense-and-respond' therapeutics aim to enlist the vast sensing repertoire of gut microbes to drive cutting-edge clinical and research applications. However, well-characterised circuit components that sense health- and disease-relevant conditions within the gut remain limited. Here, we extend the flexibility and power of a biosensor screening platform using bacterial memory circuits. We construct libraries of sensory components sourced from diverse gut bacteria using a bespoke two-component system identification and cloning pipeline. Tagging unique strains using a hypervariable DNA barcode enables parallel tracking of thousands of unique clones, corresponding to ~150 putative biosensors, in a single experiment. Evaluating sensor activity and performance heterogeneity across various in vitro and in vivo conditions using mouse models, we identify several biosensors of interest. Validated hits include biosensors with relevance for autonomous control of synthetic functions within the mammalian gut and for non-invasive monitoring of inflammatory disease using faecal sampling. This approach will promote rapid biosensor engineering to advance the development of synthetic biology tools for deployment within complex environments.