Fig. 2
Development of low-oxygen induced protein expression system in R. palustris. a The promoter activities under light-anaerobic conditions were compared by eGFP fluorescence intensities. The synthetic promoter of PT334O, the heterologous promoters of Plac and Ptac from E. coli, and the endogenous promoters of Ppuc, Ppuf, PbchP and PcrtE were analyzed. b Schematic design of low-oxygen induced protein expression based on the synthetic promoter PT334O. ORP: oxygen regular proteins, ORBS: oxygen regular protein binding site, RNAP: RNA polymerase, GOI: genes of interest. c The activities of PT334-6 and PT334O were tested at different oxygen levels. The control indicates the strain with the empty plasmid pBRT. All experiments were carried out in triplicate, and the data are presented as mean and standard deviations