초록
<B>Abstract</B><B>Background</B><P>The soil bacterium <I>Pseudomonas putida</I> is a promising platform for the production of industrially valuable natural compounds. In the case of isoprenoids, the availability of biosynthetic precursors is a major limiting factor. In <I>P. putida</I> and most other bacteria, these precursors are produced from pyruvate and glyceraldehyde 3-phosphate by the methylerythritol 4-phosphate (MEP) pathway, whereas other bacteria synthesize the same precursors from acetyl-CoA using the unrelated mevalonate (MVA) pathway.</P><B>Results</B><P>Here we explored different strategies to increase the supply of isoprenoid precursors in <I>P. putida</I> cells using lycopene as a read-out. Because we were not aiming at producing high isoprenoid titers but were primarily interested in finding ways to enhance the metabolic flux to isoprenoids, we engineered the well-characterized <I>P. putida</I> strain KT2440 to produce low but detectable levels of lycopene under conditions in which MEP pathway steps were not saturated. Then, we compared lycopene production in cells expressing the <I>Myxococcus xanthus</I> MVA pathway genes or endogenous MEP pathway genes (<I>dxs</I>, <I>dxr</I>, <I>idi</I>) under the control of IPTG-induced and stress-regulated promoters. We also tested a shunt pathway producing isoprenoid precursors from ribulose 5-phosphate using a mutant version of the <I>Escherichia coli ribB</I> gene.</P><B>Conclusions</B><P>The most successful combination led to a 50-fold increase in lycopene levels, indicating that <I>P. putida</I> can be successfully engineered to substantially increase the supply of metabolic substrates for the production of industrially valuable isoprenoids.</P>