IDENTIFICATION AND SEQUENCE-ANALYSIS OF THE GENES ENCODING A POLYKETIDE SYNTHASE REQUIRED FOR PYOLUTEORIN BIOSYNTHESIS IN PSEUDOMONAS-FLUORESCENS PF-5

Pyoluteorin is a chlorinated antifungal metabolite of mixed polyketide /amino-acid origin produced by certain strains of Pseudomonas spp., in cluding the soil bacterium Pseudomonas fluorescens Pf-5. Sequence anal ysis of a gene cluster required for pyoluteorin biosynthesis by Pf-5 ( Kraus, J., Loper, J., 1995. Appl. Environ. Microbiol. 61, 849-854) has identified two genes whose deduced peptide sequences exhibit characte ristics of both fungal and bacterial Type I polyketide synthases (PKSs ). The pyoluteorin PKS does not contain a loading domain that is typic ally present in bacterial Type I PKSs. Furthermore, this PKS possesses an acyltransferase domain that does not contain the conserved residue s surrounding the active-site motif typically found in domains of simi lar function. Based on the organization of the functional domains with in the pyoluteorin PKS, we propose a biosynthetic pathway analogous to non-aromatic polyketide biosynthesis within the Actinomycete bacteria that is responsible for the formation of the resorcinol moiety of pyo luteorin. (C) 1997 Elsevier Science B.V.