Growth rates were determined by measuring the absorbance in a Victor3 (PerkinElmer) microplate reader. Cells were grown in M9 medium supplemented with casamino acids [0.2% (w/v)] as nitrogen source and glycerol or glucose (0.5%) as carbon source. Cells were pregrown in flasks at 37°C overnight and then subjected to a 1:1000-fold dilution in fresh medium. A total of 150 μl of these diluted cultures were added to the wells of a 96-well microtiter plate (Deltalab). Absorbance values at 600 nm were taken every 7 min. These absorbance values were background subtracted and transformed into OD600 (optical density at 600 nm) values by using a calibrating curve obtained with a Shimadzu UV-1603 spectrophotometer. Growth rates (α) were obtained by fitting the growth curve between OD600 = 0.1 and OD600 = 0.3 to an exponential. Doubling times (τ) were obtained from growth rates as τ = ln(2)/α. When inducers were added to the growth medium (either arabinose or Tc), pre-inoculums were supplemented with the same concentration of inducer to be tested.

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