Optochemical Control of Bacterial Gene Expression: Novel Photocaged Compounds for Different Promoter Systems

Exploring engineered vesiculation by Pseudomonas putida KT2440 for natural product biosynthesis

Pseudomonas species have become promising cell factories for the production of natural products due to their inherent robustness. Although these bacteria have naturally evolved strategies to cope with different kinds of stress, many biotechnological applications benefit from engineering of optimised chassis strains with specially adapted tolerance traits. Here, we explored the formation of outer membrane vesicles (OMV) of Pseudomonas putida KT2440. We found OMV production to correlate with the recombinant production of a natural compound with versatile beneficial properties, the tripyrrole prodigiosin. Further, several P. putida genes were identified, whose up- or down-regulated expression allowed controlling OMV formation. Finally, genetically triggering vesiculation in production strains of the different alkaloids prodigiosin, violacein, and phenazine-1-carboxylic acid, as well as the carotenoid zeaxanthin, resulted in up to three-fold increased product yields. Consequently, our findings suggest that the construction of robust strains by genetic manipulation of OMV formation might be developed into a useful tool which may contribute to improving limited biotechnological applications.

Discovery of a Novel Photocaged PI3K Inhibitor Capable of Real-Time Reporting of Drug Release

A novel photocaged PI3K inhibitor 2 was designed and synthesized by introducing a cascade photocaging group to block its key interaction with the kinase. Upon UV light irradiation, the photocaged compound released a highly potent PI3K inhibitor to recover its anticancer properties and a fluorescent dye for real-time reporting of drug release, providing a new approach for studying the PI3K signaling transduction pathway as well as developing precisely controlled cancer therapeutics.

Light-Activated Translation of Different mRNAs in Cells via Wavelength-Dependent Photouncaging

The 5' cap is a hallmark of eukaryotic mRNA involved in the initiation of translation. Its modification with a single photo-cleavable group can bring translation of mRNA under the control of light. However, UV irradiation causes cell stress and downregulation of translation. Furthermore, complex processes often involve timed expression of more than one gene. The approach would thus greatly benefit from the ability to photo-cleave by blue light and to control more than one mRNA at a time. We report the synthesis of a 5' cap modified with a 7-(diethylamino)coumarin (CouCap) and adapted conditions for in vitro transcription. Translation of the resulting CouCap-mRNA is muted in vitro and in mammalian cells, and can be initiated by irradiation with 450 nm. The native cap is restored and no non-natural residues nor sequence alterations remain in the mRNA. Multiplexing for two different mRNAs was achieved by combining cap analogs with coumarin- and ortho-nitrobenzyl-based photo-cleavable groups.

Light-mediated control of gene expression in the anoxygenic phototrophic bacterium Rhodobacter capsulatus using photocaged inducers

Photocaged inducer molecules, especially photocaged isopropyl-β-d-1-thiogalactopyranoside (cIPTG), are well-established optochemical tools for light-regulated gene expression and have been intensively applied in Escherichia coli and other bacteria including Corynebacterium glutamicum, Pseudomonas putida or Bacillus subtilis. In this study, we aimed to implement a light-mediated on-switch for target gene expression in the facultative anoxygenic phototroph Rhodobacter capsulatus by using different cIPTG variants under both phototrophic and non-phototrophic cultivation conditions. We could demonstrate that especially 6-nitropiperonyl-(NP)-cIPTG can be applied for light-mediated induction of target gene expression in this facultative phototrophic bacterium. Furthermore, we successfully applied the optochemical approach to induce the intrinsic carotenoid biosynthesis to showcase engineering of a cellular function. Photocaged IPTG thus represents a light-responsive tool, which offers various promising properties suitable for future applications in biology and biotechnology including automated multi-factorial control of cellular functions as well as optimization of production processes.