Experiments

Replifactory can maintain continuous cultures in various modes, such as chemostat, turbidostat, morbidostat or fed phage culture lagoon.

Chemostat/Turbidostat: the culture is diluted at regular time intervals or when the OD reaches a threshold. Because the pumps are shared, discrete dilutions are used instead of a slow continuous dilution, resulting in a pseudo-turbidostat regime, where the OD drops slightly at every dilution. In the figure below the culture is diluted every 3h by adding and removing 10mL of growth medium. Smaller dilution coefficients are possible, by accurately pumping volumes as low as 0.2mL.

Morbidostat: the amount of drug medium pumped in the vial can be varied throughout the experiment. Below, the drug dose is set to 10mM, then 20mM, then 40mM, increasing stress as the culture recovers. Adjusting the stress level in response to adaptation leads to rapid evolution of resistance.

By slightly changing the tubing connections, the device can pump medium from one vial to the others. This setup can be used for “lagoon” experiments.

Phage lagoon: Yellow arrows on the graph indicate when the vial is diluted. Red arrows indicate feeding of E.coli culture to the phage vial. After feeding, the E.coli culture keeps growing for about 50 minutes, then the OD rapidly drops as they lyse. After each cycle, the lagoon is first diluted with clean LB to lower the number of phages in the vial, then they are fed with fresh exponential phase E.coli.