アジドを調節因子として用いた緑膿菌5300における電子伝達系調節とmcl-PHA生産との新規関連性

Medium chain length polyhydroxyalkanoates (mcl-PHA) are elastomeric biodegradable bioplastics produced by a few bacteria. The large-scale mcl-PHA production remains limited by the low yield of bacterial strains and biomass reduction due to prolonged nutrient limitation in the media. In the present study, Pseudomonas aeruginosa MCC 5300 produced mcl-PHA copolymer of about 39.4% cell dry weight (CDW) at a short duration of 24 h of growth in tryptic soy broth media containing oleic acid and the PHA content was enhanced up to 66.4% CDW in the presence of azide. The production of mcl-PHA at such a short duration was not reported previously in nutrient-enriched conditions. The application of azide enhanced mcl-PHA production in the bacteria. Oleic acid shifted the electron transport chain (ETC) from the cytochrome c pool to the ubiquinol pool. The inhibition of bo₃-oxidase by azide increased electron flux towards bd-oxidase to maintain proton gradient for oxidative phosphorylation, causing depletion of cellular reduced-redox cofactor levels. The increased mcl-PHA accumulation in bacteria compensated for the loss of reduced-redox cofactors, thus maintaining cellular redox homeostasis. Hence, the study invokes a novel link between the ETC and mcl-PHA production.