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Appl. Environ. Microbiol., Jun 1997, 2147-2154, Vol 63, No. 6
PE Hammer, DS Hill, ST Lam, KH Van Pee and JM Ligon
Pyrrolnitrin is a secondary metabolite of Pseudomonas and Burkholderia sp.
strains with strong antifungal activity. Production of pyrrolnitrin has
been correlated with the ability of some bacteria to control plant diseases
caused by fungal pathogens, including the damping-off pathogen Rhizoctonia
solani. Pseudomonas fluorescens BL915 has been reported to produce
pyrrolnitrin and to be an effective biocontrol agent for this pathogen. We
have isolated a 32-kb genomic DNA fragment from this strain that contains
genes involved in the biosynthesis of pyrrolnitrin. Marker-exchange
mutagenesis of this DNA with Tn5 revealed the presence of a 6.2-kb region
that contains genes required for the synthesis of pyrrolnitrin. The
nucleotide sequence of the 6.2-kb region was determined and found to
contain a cluster of four genes that are required for the production of
pyrrolnitrin. Deletion mutations in any of the four genes resulted in a
pyrrolnitrin-nonproducing phenotype. The putative coding sequences of the
four individual genes were cloned by PCR and fused to the tac promoter from
Escherichia coli. In each case, the appropriate tac promoter-pyrrolnitrin
gene fusion was shown to complement the pyrrolnitrin-negative phenotype of
the corresponding deletion mutant. Transfer of the four gene cluster to E.
coli resulted in the production of pyrrolnitrin by this organism, thereby
demonstrating that the four genes are sufficient for the production of this
metabolite and represent all of the genes required to encode the pathway
for pyrrolnitrin biosynthesis.
Copyright © 1997, American Society for Microbiology
Four genes from Pseudomonas fluorescens that encode the biosynthesis of pyrrolnitrin
Novartis Crop Protection, Inc., Research Triangle Park, North Carolina 27709, USA.
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