(35b) Modeling Growth Kinetics and Metabolism of Clostridium Acetobutylicum/Clostridium Ljungdahlii Co-Culture with Cell Fusion (Industry Candidate)

Clostridia organisms have been of interest for decades due to their unique ability to ferment a wide range of carbon sources to useful bioproducts. The metabolic repertoire of these anaerobes has been further expanded in co-cultures due to the diversity of substrates they can consume and unexpected syntrophic behaviors that are still being discovered. One such example lies in the syntrophic co-culture of Clostridium acetobutyllicum (C. ac) and C. ljungdahlii (C. lj). In addition to the discovery of an upregulation of C. lj sadh and 23bdh gene expression in the presence of C. ac (allowing C. lj to convert acetone and acetoin produced by C. ac to isopropanol and 2,3-butanediol, respectively), C. ac and C. lj cells were recently shown to fuse membranes and exchange proteomes. This work aims to characterize the resultant change in growth kinetics due to the observed fusion/protein exchange event using a kinetic model which characterizes both the pure and mixed-proteome C. ac and C. lj growth rates and the cell fusion/proteome exchange rate. The parameterized kinetic model is used to inform the construction of a community genome-scale metabolic model of pure and mixed-proteome C. ac and C. lj cells using the dynamic multi-species metabolic modeling (DMMM) framework, and characterize the dynamic shift in co-culture metabolism and redox state related to the observed fusion event required to support the experimentally measured isopropanol and 2,3-butanediol production. Single organism strain design tools (i.e. optKnock, optForce) are being adapted to support the inclusion of multi-organism models in order to understand how the C. ac and C. lj genomes can be manipulated to maximize the production of fermentation products of interest (i.e isopropanol, 2,3-butanediol) under the newly discovered C. ac/C.lj co-culture conditions.