Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 20, 2000
Publication Date: N/A
Interpretive Summary: Polyketides are a large group of biologically active compounds that are produced by bacteria and fungi. Polyketides include many well-known antibiotics used in clinical and agricultural settings. All polyketides are made by enzymes called polyketide synthases; these enzymes are synthesized using DNA sequences that are very similar among microorganisms. We used this genetic information to screen a group of insect pathogenic fungi for their potential to produce polyketides. Out of a group of 157 unique organisms, we found that at least 66 isolates have the potential to produce these compounds. This molecular screening method may be useful to identify candidates that can produce novel polyketides that might have great utility in agriculture.
Production of polyketides is accomplished through modular complex enzymes known as polyketide synthases (PKS); these enzymes have highly conserved domains that might be useful in screens for PKSs in diverse groups of organisms. A degenerate PCR-based approach was used to amplify PKS fragments of the ketosynthase domain from genomic DNA of a large group of insect-pathogenic fungi. Out of 157 genera screened, 92 isolates generate a PCR product of predicted size (~ 300 bp). The ability to detect PKS domains was a function of the number of different primer pairs employed in the screen. It is likely that PKS genes would be found in most, or all, of the fungi in this group if sufficient primer pairs were designed to identify them. Cloning and sequencing revealed that 66 isolates had at least one unique PKS sequence and ten isolates contained multiple PKS fragments, yielding a total of 76 unique PKS fragments. Since PKS homologues appear to be widespread among fungi, a PCR-based screening system appears to be an efficient, directed means to identify organisms having the potential to produce polyketides.