A Type II Polyketide Synthase is Responsible for Anthraquinone Biosynthesis in Photorhabdus luminescens

Abstract

Type II polyketide synthases are involved in the biosynthesis of numerous clinically relevant secondary metabolites with potent antibiotic or anticancer activity. Until recently the only known producers of type II PKSs were members of the Gram-positive actimomycetes, well-known producers of secondary metabolites in general. Here we present the second example of a type II PKS from Gram-negative bacteria. We have identified the biosynthesis gene cluster responsible for the production of anthraquinones (AQs) from the entomopathogenic bacterium Photorhabdus luminescens. This is the first example of AQ production in Gram-negative bacteria, and their heptaketide origin was confirmed by feeding experiments. Deletion of a cyclase/aromatase involved in AQ biosynthesis resulted in accumulation of mutactin and dehydromutactin, which have been described as shunt products of typical octaketide compounds from streptomycetes, and a pathway for AQ formation from octaketide intermediates is discussed.

Elucidation of the Photorhabdus temperata Genome and Generation of a Transposon Mutant Library To Identify Motility Mutants Altered in Pathogenesis

“…S3 in the supplemental material), which was predicted to contain the ant-ABCDEFGHI operon. The genes in this operon were highly homologous to the ant operon found in P. luminescens and identically organized (62). This ant operon was not found in the P. asymbiotica genome, but the remnants of 4 genes were present.…”

Cinnamic Acid, an Autoinducer of Its Own Biosynthesis, Is Processed via Hca Enzymes in Photorhabdus luminescens

“…Unlike most known enterobacteria, P. luminescens expresses a PAL enzyme, catalyzing CA formation from phenylalanine (41). CA was previously detected in bacterial extracts (5). The presence of CA in the culture supernatants of TT01R grown in LB medium was analyzed by HPLC.…”

Bacterial Biosynthesis of a Multipotent Stilbene

“…The genes bkdA, bkdB and bkdC were deleted using a previously described PCR based technique. [12] Briefly, for each gene, the appropriate L1 and L2 primers were used to amplify a region immediately upstream from the gene to be deleted (i.e. lefthand flanking region).…”

“…[12] Briefly, an internal fragment (~600 bp) from these genes was amplified by PCR using primers with SphI and SacI restriction sites and the resulting fragment was then cloned into pDS132. The final constructs were then conjugated into TT01 rif as described above and mutants were verified using two PCR primers lying outside the amplified region and two primers specific for the vector backbone as described.…”

“…Briefly, [1-13 C]acetate and [1,2-13 C 2 ]acetate (both at 0.5 gL -1 with 99% of 13 C-enrichment [Sigma-Aldrich]) were added in three equal portions over three days to a LB culture of strain TT01 (1 L) grown in a 5 L-flask with Amberlite XAD-16 (2 %) and 1 was isolated from the XAD-16 crude extract by sequential chromatography as described previously. [12] Labelling was observed for C-1/C-3 and C-4/C-6 and from the different ratio of 13 C-enriched doublet to central signal of these carbons (Table S1, Figure S2), it is evident that only one intact acetate unit is incorporated (eg. C-6?C -1) and that the second phenolic carbon (eg.…”