Enhanced PrrAB system activation and restricted farnesyl pyrophosphate diversion underlie high coenzyme Q10 accumulation in Rhodobacter sphaeroides HY01

The industrial Rhodobacter sphaeroides HY01 accumulates an exceptionally high level of coenzyme Q₁₀ (Q₁₀), but the underlying mechanisms remain incompletely understood. Given the central role of Q₁₀ in respiratory electron transport, previous observation of reduced expression of cbb₃-type cytochrome c oxidase genes in HY01 suggested a potential mechanistic link. In this study, we found that cbb₃ oxidase activity in HY01 was only 21.8–32.8 % of that in the wild-type 2.4.1, and restoring this activity led to a 64.4 % decrease in Q₁₀ accumulation, demonstrating a strong inverse correlation. This correlation was found to be mediated by the activation of the PrrAB two-component regulatory system, which is negatively regulated by cbb₃ oxidase. However, disruption of cbb₃ oxidase in 2.4.1 alone was insufficient to reproduce the high Q₁₀ accumulation phenotype, indicating that additional factors may be required. Previous research also revealed restricted synthesis of geranylgeranyl diphosphate (GGPP) in HY01, which likely reduces the diversion of the Q₁₀ precursor farnesyl diphosphate (FPP). Reconstituting this metabolic constraint in wild-type strain, combined with fine-tuning of PrrAB system activation, resulted in up to a 218.0 % increase in Q₁₀ accumulation, achieving a level nearly identical to HY01. Combining mechanistic investigation and inverse metabolic engineering, this study demonstrates that the high Q₁₀ accumulation in HY01 results from the synergistic effects of enhanced PrrAB activation and restricted FPP diversion, providing new insights into the key factors underlying high-level Q₁₀ accumulation in R. sphaeroides.