Effect of Photocaged Isopropyl β-d-1-Thiogalactopyranoside Solubility on Light-Responsiveness of LacI-controlled Expression Systems in Different Bacteria.

Photolabile protecting groups play a significant role for controlling biological functions and cellular processes in living cells and tissues, since light offers a high spatiotemporal control, is non-invasive as well as easily tuneable. In the recent past, photo-responsive inducer molecules such as 6-nitropiperonyl-caged IPTG (NP-cIPTG) have been used as optochemical tools for Lac repressor controlled microbial expression systems. To further expand the applicability of the versatile optochemical on-switch, we now investigated if the modulation of cIPTG water solubility can improve the light-responsiveness of appropriate expression systems in bacteria. To this end, we developed two new cIPTG derivatives with varying hydrophobicity and demonstrated both an easy applicability for the light-mediated control of gene expression and a simple transferability of this optochemical toolbox to the biotechnologically relevant bacteria Pseudomonas putida and Bacillus subtilis . Notably, the more water-soluble cIPTG derivative has proven to be particularly suitable for light-mediated gene expression in these alternative expression hosts.