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J. Bacteriol., 12 1997, 7360-7368, Vol 179, No. 23
KT Seow, G Meurer, M Gerlitz, E Wendt-Pienkowski, CR Hutchinson and J Davies
To examine as randomly as possible the role of the beta-ketoacyl and acyl
carrier protein (ACP) components of bacterial type II polyketide synthases
(PKSs), homologs of the chain-length-factor (CLF) genes were cloned from
the environmental community of microorganisms. With PCR primers derived
from conserved regions of known ketosynthase (KSalpha) and ACP genes
specifying the formation of 16- to 24-carbon polyketides, two CLF (KSbeta)
genes were cloned from unclassified streptomycetes isolated from the soil,
and two were cloned from soil DNA without the prior isolation of the parent
microorganism. The sequence and deduced product of each gene were distinct
from those of known KSbeta genes and, by phylogenetic analysis, belonged to
antibiotic-producing PKS gene clusters. Hybrid PKS gene cassettes were
constructed with each novel KSbeta gene substituted for the actI-ORF2 or
tcmL KSbeta subunit genes, along with the respective actI-ORF1 or tcmK
KSalpha, tcmM ACP, and tcmN cyclase genes, and were found to produce an
octaketide or decaketide product characteristic of the ones known to be
made by the heterologous KSalpha gene partner. Since substantially less
than 1% of the microorganisms present in soil are thought to be
cultivatable by standard methods, this work demonstrates a potential way to
gain access to a more extensive range of microbial molecular diversity and
to biosynthetic pathways whose products can be tested for biological
applications.
Copyright © 1997, American Society for Microbiology
A study of iterative type II polyketide synthases, using bacterial genes cloned from soil DNA: a means to access and use genes from uncultured microorganisms
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