The variation of promoter strength in different gene contexts

Background Promoter engineering has been employed as a strategy to enhance and optimize the production of bio-products. There have been many effortless studies searching the best promoter for biological application. However, whether promoter strengths stay unchanged in different gene contexts remains unknown. Results Six consecutive promoters at different strength levels were used to construct six different versions of plasmid backbone pTH1227, followed by inserted genes encoding two polymer-producing enzymes. Some of promoter strengths in the presence of inserted sequences did not correspond to the reported strengths in a previous study. When removing the inserted sequences, the strengths of these promoters returned to their reported strengths. These changes were further confirmed to occur at transcriptional levels. Polymer production using our newly constructed plasmids showed polymer accumulation levels relatively corresponding to the promoter strengths reported in our study. Conclusion Our study revealed the essence of re-assessing promoter strength in a specific gene context. Different gene contexts could result in the variation of promoter strengths, hence this might lead to different outcomes in downstream applications.