(711d) Tools for Engineering Coordinated System Behaviour in Synthetic Microbial Consortia

Engineering synthetic microbial communities requires the development of multiple orthogonal cell-to-cell communication channels to propagate information with minimal signal interference. Here we focus on quorum sensing, a natural bacterial mechanism for coordinating population behaviour. Previous studies have largely focused on reducing signal leakage between systems of transcription factors and cognate signalling molecules, e.g. by the discovery of new systems with structurally diverse signalling molecules. However, the intentional use of non-cognate pairs as a design feature has received limited attention so far. We began by characterising the largest library of acyl homoserine lactone receiver devices date, quantifying all cognate and non-cognate chemical signal interactions of six devices constructed using genetic parts mined from various microbial species. The input-output responses were then parametrised in terms of their basal expression, maximal expression, fold activation, input signal EC50 concentration for half-activation and device sensitivity. Building on this database of 36 synthetic quorum systems (cognate and non-cognate pairs), we developed a software tool that allows automated selection of orthogonal chemical channels. We used our approach to identify a potential system using up to four orthogonal channels simultaneously. The software can flexibly accommodate user-defined constraints for fold changes in gene expression and identify any number of desired communication channels, which can be particularly useful in enabling consortia designs of increasing complexity as the number of characterised quorum systems expands. Furthermore, we experimentally validated one of the software predictions by engineering a polyclonal co-culture capable of controlling gene expression using three non-interfering AHL communication channels. The development of multiple non-interfering cell-to-cell communication channels is an enabling step that facilitates the design of synthetic microbial consortia for novel applications including distributed bio-computation, increased bioprocess efficiency, cell specialisation, and spatial organisation.