C-4-Modified Isotetrones Prevent Biofilm Growth and Persister Cell Resuscitation in Mycobacterium smegmatis

Hyperphosphorylatednucleotide (p)-ppGpp, synthesized by Rel protein,regulates the stringent response pathway responsible for biofilm andpersister cell growth in mycobacteria. The discovery of vitamin Cas an inhibitor of Rel protein activities raises the prospect of tetronelactones to prevent such pathways. The closely related isotetronelactone derivatives are identified herein as inhibitors of the aboveprocesses in a mycobacterium. Synthesis and biochemical evaluationsshow that an isotetrone possessing phenyl substituent at C-4 inhibit the biofilm formation at 400 mu g mL(-1), 84 h post-exposure, followed by moderate inhibition by the isotetronepossessing the p-hydroxyphenyl substituent. The latterisotetrone inhibits the growth of persister cells at 400 mu gmL(-1) f.c. when monitored for 2 weeks, under PBSstarvation. Isotetrones also potentiate the inhibition of antibiotic-tolerantregrowth of cells by ciprofloxacin (0.75 mu g mL(-1)) and thus act as bioenhancers. Molecular dynamics studies show thatisotetrone derivatives bind to the Rel(Msm) protein moreefficiently than vitamin C at a binding site possessing serine, threonine,lysine, and arginine.

Automated summary

The discovery of vitamin C as an inhibitor of Rel protein activities raises the prospect of tetronelactone derivatives to prevent biofilm and persister cell growth in mycobacteria. In this study, isotetronelactone derivatives were found to inhibit these processes in mycobacterium, with the isotetrone possessing a phenyl substituent at C-4 showing the strongest inhibition of biofilm formation, followed by moderate inhibition by the isotetrone with the p-hydroxyphenyl substituent. The latter isotetrone also inhibits the growth of persister cells.