Biological demands and toxicity of isoprenoid precursors in Bacillus subtilis through cell-permeant analogs of isopentenyl pyrophosphate and dimethylallyl pyrophosphate.

Bacterial isoprenoids are necessary for many biological processes, including maintaining membrane integrity, facilitating intercellular communication, and preventing oxidative damage. All bacterial isoprenoids are biosynthesized from two five carbon structural isomers, isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), which are cell impermeant. Herein, we demonstrate exogenous delivery of IPP and DMAPP into Bacillus subtilis by utilizing a self immolative ester (SIE)-caging approach. We initially evaluated native B. subtilis esterase activity, which revealed a preference for short straight chain esters. We then examined the viability of the SIE-caging approach in B. subtilis and demonstrate that the released caging groups are well tolerated and the released IPP and DMAPP are bioavailable, such that isoprenoid biosynthesis can be rescued in the presence of pathway inhibitors. We further show that IPP and DMAPP are both toxic and inhibit growth of B. subtilis at the same concentration. Lastly, we establish the optimal ratio of IPP to DMAPP (5:1) for B. subtilis growth and find that, surprisingly, DMAPP alone is insufficient to rescue isoprenoid biosynthesis. These findings showcase the potential of the SIE-caging approach in B. subtilis and promise to both aid in novel isoprenoid discovery and to inform metabolic engineering efforts in bacteria.