Effect of carbohydrates on mycolactone biosynthesis gene expression in <i>M. ulcerans</i>.

<p><b>A-</b> Schematic representation of mycolactone biosynthesis genes and representation of their function on the mycolactone structure <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002502#pntd.0002502-Stinear1" target="_blank">[9]</a>, <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002502#pntd.0002502-Stinear2" target="_blank">[10]</a>. The six genes coding for proteins involved in mycolactone synthesis are located on the giant plasmid named pMUM001. The genes <i>mlsA1</i> (50,973 bp) and <i>mlsA2</i> (7,233 bp) encode modular type I polyketide synthase (PKS) required for the biosynthesis of the mycolactone core (highlighted in orange). The side chain enzyme is encoded by <i>mlsB</i> gene (42,393 bp) in pink. The <i>mls</i> genes encode 11 different functional domains that are repeated along the gene. Among these modules, the two load modules (LM, in black) are present at 5′end of <i>mlsA1</i> and <i>mlsB</i> genes and 15 ketoreductase (KR, in grey) are present. There are also three genes coding for potential polyketide-modifying enzymes, including a P450 hydroxylase (<i>mup053</i>, in purple), probably responsible for hydroxylation at carbon 12 of the side chain, a potential FabH-like type III ketosynthases (KS) with an acyltransferase activity that might catalyze the C–O bond between the mycolactone core and side-chain (<i>mup045</i>, in green) and a putative type II thioesterase (<i>mup038</i>, in blue) that may be required for removal of short acyl chains from the PKS loading modules, arising by aberrant decarboxylation. <b>B-</b> Analysis of mycolactone-associated gene expression in <i>M. ulcerans</i> grown on various 7.5% sugar-enriched medium by qRT-PCR. Gene expression has been normalized to the constitutively expressed housekeeping gene <i>ppk</i> encoding the polyphosphate kinase. Relative genes expression is expressed as fold-changes relative to the 7H10 medium. Data are presented as the mean and SD of at least three biological repeats. LM, load module domain.