Fig. 5.
EcoMsbA secretes β-carotene. The assay was performed, and the results were analyzed and are presented in a manner identical to the description in legend to Fig. 3. (A and B) Secreted β-carotene was quantified (A-absorbance at λmax – 453 nm) in the decane phase after 144-h incubation at 30 °C, with aeration at 250 rpm, and was significantly higher for EcoMsbA-expressing cells compared with nonexpressing control (n = 3 biological repeats ± SEM; Student t test as in the legend to Fig. 3). Control was indistinguishable from background, probably due to the relatively lower expression of genomic MsbA and negligible passive diffusion of β-carotene, but was nevertheless quantified for uniformity. (C) No significant differences (P > 0.11) were observed in the intracellular produced amounts of β-carotene between EcoMsbA-expressing and nonexpressing cells.