The potential of nonmodel organisms for industrial biotechnology is increasingly becoming evident since advances in systems and synthetic biology have made it possible to explore their unique traits. However, the lack of adequately characterized genetic elements that drive gene expression impedes benchmarking nonmodel with model organisms. Promoters are one of the genetic elements that contribute significantly to gene expression, but information about their performance in different organisms is limited. This work addresses this bottleneck by characterizing libraries of synthetic σ70-dependent promoters controlling the expression of msfGFP, a monomeric, superfolder green fluorescent protein, in both Escherichia coli TOP10 and Pseudomonas taiwanensis VLB120, a less explored microbe with industrially attractive attributes. We adopted a standardized method for comparing gene promoter strength across species and laboratories. Our approach uses fluorescein calibration and adjusts for cell growth variation, enabling accurate cross-species comparisons. The quantitative description of promoter strength is a valuable expansion of P. taiwanensis VLB120's genetic toolbox, while the comparison with the performance in E. coli facilitates the evaluation of P. taiwanensis VLB120's potential as a chassis for biotechnology applications.
Keywords: Pseudomonads; expression strength; fluorescent reporter; genomic integration; metabolic engineering; promoter engineering; synthetic biology.