Functional replacement of isoprenoid pathways in Rhodobacter sphaeroides

Summary Advances in synthetic biology and metabolic engineering have proven the potential of introducing metabolic by‐passes within cell factories. These pathways can provide a more efficient alternative to endogenous counterparts due to their insensitivity to host's regulatory mechanisms. In this work, we replaced the endogenous essential 2‐C‐methyl‐D‐erythritol 4‐phosphate (MEP) pathway for isoprenoid biosynthesis in the industrially relevant bacterium Rhodobacter sphaeroides by an orthogonal metabolic route. The native 2‐C‐methyl‐D‐erythritol 4‐phosphate (MEP) pathway was successfully replaced by a heterologous mevalonate (MVA) pathway from a related bacterium. The functional replacement was confirmed by analysis of the reporter molecule amorpha‐4,11‐diene after cultivation with [4‐13C]glucose. The engineered R. sphaeroides strain relying exclusively on the MVA pathway was completely functional in conditions for sesquiterpene production and, upon increased expression of the MVA enzymes, it reached even higher sesquiterpene yields than the control strain coexpressing both MEP and MVA modules. This work represents an example where substitution of an essential biochemical pathway by an alternative, heterologous pathway leads to enhanced biosynthetic performance.
This work describes the design and implementation of pathway replacement in isoprenoid metabolism in the bacterium Rhodobacter sphaeroides. Integration of a heterologous mevalonate pathway was followed by the inactivation of the endogenous MEP pathway via Cas9 counter‐selection. The resulting strain showed increased amorphadiene yields compared to the parental strain. Therefore replacement of endogenous pathways with non‐native counterparts is suggested for rational design of microbial cell factories.