Involvement of the AtoSCDAEB regulon in the high molecular weight poly-(R)-3-hydroxybutyrate biosynthesis in phaCAB+ Escherichia coli

AtoSC two-component system plays a pivotal role in many regulatory indispensable Escherichia coli processes. AtoSCDAEB regulon, comprising the AtoSC system and the atoDAEB operon, regulates the short-chain fatty acids catabolism. We report here, that AtoSC up-regulates the high-molecular weight PHB biosynthesis, in recombinant phaCAB+ E. coli, with the Cupriavidus necator phaCAB operon. PHB accumulation was maximized upon the acetoacetate-mediated induction of AtoSC, under glucose 1% w/v, resulting in a yield of 1.73 g/l with a biopolymer content of 64.5% w/w. The deletion of the atoSC locus, in the ΔatoSC strains, resulted in a 5 fold reduction of PHB accumulation, which was restored by the extrachromosomal introduction of the AtoSC system. The deletion of the atoDAEB operon triggered a significant decrease in PHB synthesis in ΔatoDAEB strains. However, the acetoacetate-induced AtoSC system in those strains increased PHB to 1.55 g/l, while AtoC expression increased PHB to 1.4 g/l upon acetoacetate. The complementation of the ΔatoDAEB phenotype was achieved by the extrachromosomal introduction of the atoSCDAEB regulon. The individual inhibition of β-oxidation and mainly fatty-acid biosynthesis pathways by acrylic acid or cerulenin respectively, reduced PHB biosynthesis. Under those conditions the introduction of the atoSC locus or the atoSCDAEB regulon was capable to up-regulate the biopolymer accumulation. The concurrent inhibition of both the fatty acids metabolic pathways eliminated PHB production. PHB up-regulation in phaCAB+ E. coli, by AtoSC signaling through atoDAEB operon and its participation in the fatty acids metabolism interplay, provide additional perceptions of AtoSC critical involvement in E. coli regulatory processes towards the biotechnologically improved polyhydroxyalkanoates biosynthesis.