Biosynthetic Olfactory System from Multiplexed Engineered Microbes (BOSMEM)

Whole-cell biosensors can detect many types of chemicals in complex environments, but existing designs force a tradeoff in multiplexed sensing: separating sensor strains into individual reservoirs limits how many analytes can be monitored at once, while pooling strains in open co-culture lets faster-growing strains take over within days, corrupting the signal. The microfluidic "mother machine" has been used for over a decade, mostly to study individual bacterial strains with single-cell resolution, but never to house multiple engineered strains simultaneously for sensing applications. We repurpose this device to hold a library of genetically distinct biosensor strains, physically isolating each strain in its own growth channel while continuous flow keeps every strain fed. Each strain reports on a target chemical through a unique combination of three fluorescent proteins, so seven distinguishable signals emerge from only three optical channels. We characterized turn-on and turn-off kinetics of several biosensors in the mother machine. Over a multi-day experiment with repeated chemical exposures, biosensors housed this way matched the expected on/off state and held stable population ratios, while biosensors in an open batch co-culture drifted and lost reliable signal. This establishes mother-machine-based multiplexing as a scalable route to long-term chemical monitoring with living sensors.