Metabolic diversity in myxobacteria: identification of the myxalamid and the stigmatellin biosynthetic gene cluster of Stigmatella aurantiaca Sg a15 and a combined polyketide-(poly)peptide gene cluster from the epothilone producing strain Sorangium cellulosum So ce90

Myxobacterial strains producing polyketides (PKs) assumed to be biosynthesi zed by a type I polyketide synthase (PKS) were analysed. Myxobacteria also produce a variety of polypeptides (PP) and PKs with incorporated amino acid s ('mixed PK-PP'). In order to be able to identify the biosynthetic gene cl usters for these metabolites a PCR based approach has been developed to clo ne ketosynthase (KS) domains of PKS genes from these organisms. Conserved r egions of peptide synthetases of the non-ribosomal type (NRPS) were also am plified via PCR. KS fragments from Stigmatella aurantiaca Sg a15 were used for chromosomal gene inactivation experiments resulting in a series of muta nts including such that were unable to produce stigmatellins and myxalamids . A NRPS fragment and PKS fragments from Sorangium cellulosum So ce90 were used to identify cosmids hybridizing with both types of probes from a genom ic library. Both a NRPS and a PKS fragment were cloned and sequenced from a relatively short restriction fragment of one of these cosmids. The method described here should be very useful to clone and identify PKS, NRPS and mi xed PKS-NRPS from myxobacteria in general and thereby open opportunities to use the biochemical diversity of these bacteria for genetic engineering an d combinatorial biosynthesis. (C) 1999 Elsevier Science B.V. All rights res erved.