Development of a Growth Kinetic Model for Biocontained Members of a Synthetic Consortia

Intrinsic biological containment approaches offer many advantages in synthetic consortia, such as the ability to control the growth rates and abundance of individual engineered species as well as the mitigation of the risk of unintended proliferation of engineered species in the environment. To work towards ensuring robust biological containment in preparation for environmental release, we developed a growth model to predict the behavior of an intrinsically biocontained microbial strain that is dependent on an orthogonal nutrient for growth. We first demonstrate the tight growth dependence of the strain on a limiting, required metabolite using non-interactive double-substrate limited growth kinetics. To understand the behavior of the biocontained strain in co-culture, we modeled a pairwise interaction of two bacterial strains, one of which is biocontained, and estimated the ability to tune co-culture composition based on the concentration of the required metabolite. Ultimately, we advance towards a quantitative framework for estimating the growth dynamics of a co-culture that features a newly engineered microbial interaction, an obligate and orthogonal commensalism. This model can currently provide qualitative predictions of the impact of inoculation ratio and substrate concentration on the growth of the orthogonally obligate commensal, which should provide a foundation for studying orthogonal biological dependence and biocontained members of synthetic ecologies.