Carotenoid production
To determine the carotenoid content of cells, P. ananatis strains were grown in 5 mL of LB medium at 28°C. Cells were harvested by centrifugation at 10,000 × g for 1 min and suspended in 1ml of methanol. The samples were vortexed for 10 min and centrifuged at 10,000 × g for 10 min, and the methanol supernatant containing carotenoids was transferred to a new tube. We quantified the carotenoid content of the extracts by measuring the absorbance at 450 nm using a Genesys 10S UV-VIS spectrophotometer (Thermo Fisher Scientific).