Toward an “artificial cell” on a chip: Cell-free systems that reconstitute biochemical pathways have been critical for unraveling the inner workings of the cell. Karzbrun et al. created a highly miniaturized cell-free system on a silicon chip. A series of tiny linked compartments were fabricated on the chip, in which DNA-driven reactions occurred, with materials flowing into and diffusing between the compartments. The system recreated oscillating protein expression patterns and protein gradients, and provides a stepping stone to creating “artificial cells” on a chip. Science , this issue p. 829

A complete gene expression reaction is reconstituted in a cell-free system comprising the entire endogenous transcription, translation, as well as mRNA and protein degradation machinery of E. coli. In dissecting the major reaction steps, we derive a coarse-grained enzymatic description of biosynthesis and degradation, from which ten relevant rate constants and concentrations are determined. Governed by zeroth-order degradation, protein expression follows a sharp transition from undetectable levels to constant-rate accumulation, without reaching steady state.

Significance: Synchrony, entrainment, and pattern formation are nonlinear modes of communication and collective behavior in living systems across scales. We aim to understand these complex processes by building them bottom-up in a minimal environment to unravel basic rules governing their behavior. However, it has so far been challenging to emulate spatially distributed coupled gene expression cellular reactions. We show a microfluidic device of a confined coupled system of DNA compartments programmed with nonlinear genetic oscillator and diffusion-based communication. This approach provides unique control of experimental parameters, which reveals a rich phenomenology of cell-free gene expression patterns in space and time.