Protocols

In this section you will find detailed protocols of experimental procedures.

Recipes for Solutions and Media

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E. Coli Continuous Cultivation

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Overnight cultures in 20 mL 2xYT medium containing chloramphenicol were inoculated directly from -80°C glycerol cell stock. Cells were grown in non-baffled-flasks at 37°C and 250 rpm.
The next day, main cultures in 75 mL 2xYT medium containing ampicillin were inoculated from overnight cultures to an OD520=0.5. Growth of each strain was observed with and without induction of the promoters regulation the ampicillin resistance gene. All cultures and measurements were conducted as duplicates.
For the induction of beta-lactamase (ampR) expression by pRhl und pLas autoinducers n-buturyl-homoserinlactone and n-oxododecanoyl-homoserinlactone were added respectively to a final concentration of 10 µmol/L. Cells were grown in non-baffled flasks at 37°C and 250 rpm.
Samples from each flask were taken at appropriate times depending on the growth phase of the cells. Optical density was measured at a wavelength of 520 nm in order to avoid/minimize absorption by the chromoproteins (see absorption spectra). Cells were left to grow until the stationary phase was reached.