(329d) Transcriptomic Studies of an Amorphadiene Producing E. Coli Strain in an Acka/Pta/Poxb Deletion Background

The engineered production of the precursors to the anti-malarial drug, artemisinin, via the exogenous mevalonate pathway in Escherichia coli branches from the central carbon metabolic pathway at acetyl Co-A. In an attempt to increase production by directing carbon flow through the pathway, knockouts of the pathways converting acetyl Co-A to acetate, ackA/pta/poxB, were created in a DH1 background. Acetate is also a major fermentation product under conditions of excess glucose, which leads to lower pH and slower growth. Thus, an acetate pathway knockout might be a suitable host strain for large-scale production. This system presents a unique opportunity to study the transcriptional burden of simultaneously expressing a full exogenous pathway to produce a secondary metabolite. The coordinated overexpression of an entire pathway presents a large burden on the cell's physiology, both in depleting nutrients and introducing foreign intermediates which could have toxic side-effects. Transcriptomic tools, including microarrays and quantitative PCR, were used to study the transcriptional responses of both the endogenous and exogenous genes as a result of inducing the pathway in both the wild type and the acetate knockout DH1 strain. We present the time course and inter-strain gene expression comparisons along with the concentrations of the pathway endpoint and intermediate, acetate, and growth rate.