Transcriptional analysis of genes from the clavulanic acid biosynthetic gene cluster (BGC) in wt <i>S</i>. <i>clavuligerus</i> and the <i>Δcpe-INF</i> mutant.

(A) The overall architecture of the BGC is shown with each hollow arrow representing a gene and the arrowhead its orientation. The known transcriptional units are also indicated, and the broken lines represent transcripts (B) The first gene from each transcriptional unit in (A) was selected for analysis to determine its comparative expression level in the two respective strains. RNA isolated from wt S. clavuligerus and the Δcpe-INF mutant after 48 hours of growth in SA medium was used for RT-PCR (+) analysis. As controls, treated RNA samples were used directly in PCR without RT or cDNA synthesis (-). The expression of the constitutively expressed hrdB gene (extreme right boxed panel) was used as internal control to normalize expression levels between different samples/strains.