(67g) Yeast Artificial Cell-Cell Communication and Conway's Game-of-Life in Yeast

In nature, programmed cell death is often used to remove excess cells, as is seen in embryo, finger, and brain development, sea urchin metamorphosis, and in plant immune responses. Within the context of synthetic biology, coordinating cell death and survival artificially will enhance our understanding of natural systems and our ability to engineer complex cellular patterns. In addition, the ability to precisely regulate yeast cell density is essential for numerous industrial applications, such as yeast fermentation. To explore coordination of cell death and survival in a pattern formation system, we are implementing a genetic version of Conway's Game of Life. As with the computer version of the game, cells die due to overpopulation (too many neighbors) or when they are in solitude (too few neighbors). Otherwise, cells are allowed to survive and proliferate if they have the appropriate number of neighbors. Our expectation is that 2D patterns with certain predictable properties will emerge after repeated rounds of cell death and survival. By demonstrating how changes to the underlying survival rules alter the resulting global patterns, we can improve our understanding of how complex global behavior emerges from the interaction of elements governed by simple local rules. Towards this goal, three biological devices are designed and engineered, and integrated into yeast cellular machinery, namely a quorum sensing device, a low threshold killing device, and a high threshold killing device. The quorum sensing device (QS) is designed by integrating a ?sender' part and a ?receiver' part abstracted from Arabidopsis thaliana into Saccharomyces cerevisiae. The low threshold killing device (LT) is based on the interaction between the apoptotic protein Bax and its counterpart Bcl-xL, that is Bax alone can kill yeast cells and Bcl-xL can rescue cell death by blocking Bax from functioning. Different from the low threshold, the high threshold killing device (HT) functions by conditionally expressing Cre recombinase to delete a critical gene in cell wall integrity, which is flanked by two LoxP sites. Based on experimental results, the low threshold killing device and the high threshold killing device have a four-fold and three-fold killing efficiency respectively. Current efforts are focused on the fine-tuning of the two killing devices to have a nice survival band-pass.