Insect‐Associated Bacteria Assemble the Antifungal Butenolide Gladiofungin by Non‐Canonical Polyketide Chain Termination

Niehs, Sarah P.; Kumpfmüller, Jana; Dose, Benjamin; Little, Rory F; Ishida, Keishi; Flórez, Laura; Kaltenpoth, Martin; Hertweck, Christian

doi:10.1002/anie.202005711

Cited by 38 publications

(43 citation statements)

References 43 publications

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“…2B) based on the gene structure of PHM037. In analogy to biochemically characterized glutaramide assembly in gladiofungin molecule (17), the loading module composed of the amidotransferase SbnJ and the ACP SbnK is responsible for transferring the amino group from amino acid substrate, likely glutamine, to activated malonate. The complete glutaramide starting unit is further generated with the aid of the first 2 modules in the PKS SbnO.…”

Section: Resultsmentioning

confidence: 99%

“…Known glutarimide polyketides have been isolated from actinomycetes (12)(13)(14)(15)(16) with the exception of recently identified gladiofungin from Burkholderia gladioli (17). Nevertheless, the production of the sesbanimide analogs has been attributed to Gram-negative bacteria, i.e., marine Agrobacterium strains, PH-103 and PH-A034C, isolated from the tunicates Ecteinascidia turbinata collected in Florida and Polycitonidae sp.…”

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confidence: 99%

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Identification of trans-AT polyketide clusters in two marine bacteria reveals cryptic similarities between distinct symbiosis factors

Kačar

Cañedo

Rodríguez

et al. 2020

Preprint

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Glutaramide-containing polyketides are known as potent antitumoral and antimetastatic agents. However, the associated gene clusters have only been identified and studied in a few Streptomyces producers and sole Burkholderia gladioli symbiont. The new glutaramide-family polyketides, denominated sesbanimides D, E and F along with the previously known sesbanimide A and C, were isolated from two marine alphaproteobacteria Stappia indica PHM037 and Labrenzia aggregata PHM038. Structures of the isolated compounds were elucidated based on 1D and 2D homo and heteronuclear NMR analyses and ESI-MS spectrometry. All compounds exhibited strong antitumor activity in lung, breast and colorectal cancer cell lines. Subsequent whole genome sequencing and genome mining revealed the presence of the trans-AT PKS gene cluster responsible for the sesbanimide biosynthesis, described as sbn cluster, and the sesbanimide modular assembly is proposed. Interestingly, numerous homologous orphan gene clusters were localized in distantly related bacteria and used as comparative genomic assets for a more global characterization of sbn like-clusters. Strikingly, the modular architecture of downstream mixed type PKS/NRPS, SbnQ, revealed high similarity to PedH in pederin and Lab13 in labrenzin gene clusters, although those clusters are responsible for the production of structurally completely different molecules. The unexpected presence of SbnQ homologs in unrelated polyketide gene clusters across phylogenetically distant bacteria, raises intriguing questions about the evolutionary relationship between glutaramide-like and pederin-like pathways, as well as the functionality of their synthetic products.SignificanceGlutaramide-containing polyketides are still a largely understudied group of polyketides, produced mainly by the genera Streptomyces, with a great potential for antitumor drug production. Here, we describe genomes of two cultivable marine bacteria, Stappia indica PHM037 and Labrenzia aggregata PHM038, producers of the cytotoxic glutaramide-family polyketides sesbanimide A and C with chemical elucidation of newly identified analogs D, E and F. Genome mining revealed trans-AT PKS gene cluster responsible for sesbanimide biosynthesis. Although there are numerous homologous gene clusters present in remarkably different bacteria, this is the first time that the biosynthesis product has been reported. The comparative genome analysis reveals stunning, cryptic evolutionary relationship between sesbanimides, glutaramides from Streptomyces spp. and the pederin-family gene clusters.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Identification of trans-AT polyketide clusters in two marine bacteria reveals cryptic similarities between distinct symbiosis factors

Kačar

Cañedo

Rodríguez

et al. 2020

Preprint

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“…Several possible genes for SRB biosynthesis and antibiotic regulation were found around srrX ( orf85 ) on pSLA2-L; the NAD-dependent dehydrogenase gene srrG ( orf81 ), the phosphatase gene srrP ( orf83 ), the P450 monooxygenase gene srrO ( orf84 ), and the thioesterase gene srrH ( orf86 ), together with repressor genes srrA ( orf82 ) and srrB ( orf79 ). The possible biosynthetic pathway of SRBs were shown in Figure 7 based on the biosynthetic pathways for other signaling molecules, A-factor in S. griseus [ 8 ] and virginia butanolides in S. virginiae [ 43 ], and antifungal butenolide gladiofungin in Burkholderia gladioli HKI0739 [ 44 ]. Medium-chain (C 12 or C 13 ) β-keto acid was derived through fatty acid biosynthesis pathway; four units of malonyl CoA are condensed with either an isobutyryl CoA unit for SRB1 or a 2-methylbutyryl CoA unit for SRB2.…”

Section: Discussionmentioning

confidence: 99%

Functional Analysis of P450 Monooxygenase SrrO in the Biosynthesis of Butenolide-Type Signaling Molecules in Streptomyces rochei

et al. 2020

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Streptomyces rochei 7434AN4 produces two structurally unrelated polyketide antibiotics lankacidin and lankamycin, and their biosynthesis is tightly controlled by butenolide-type signaling molecules SRB1 and SRB2. SRBs are synthesized by SRB synthase SrrX, and induce lankacidin and lankamycin production at 40 nM concentration. We here investigated the role of a P450 monooxygenase gene srrO (orf84), which is located adjacent to srrX (orf85), in SRB biosynthesis. An srrO mutant KA54 accumulated lankacidin and lankamycin at a normal level when compared with the parent strain. To elucidate the chemical structures of the signaling molecules accumulated in KA54 (termed as KA54-SRBs), this mutant was cultured (30 L) and the active components were purified. Two active components (KA54-SRB1 and KA54-SRB2) were detected in ESI-MS and chiral HPLC analysis. The molecular formulae for KA54-SRB1 and KA54-SRB2 are C15H26O4 and C16H28O4, whose values are one oxygen smaller and two hydrogen larger when compared with those for SRB1 and SRB2, respectively. Based on extensive NMR analysis, the signaling molecules in KA54 were determined to be 6′-deoxo-SRB1 and 6′-deoxo-SRB2. Gel shift analysis indicated that a ligand affinity of 6′-deoxo-SRB1 to the specific receptor SrrA was 100-fold less than that of SRB1. We performed bioconversion of the synthetic 6′-deoxo-SRB1 in the Streptomyces lividans recombinant carrying SrrO-expression plasmid. Substrate 6′-deoxo-SRB1 was converted through 6′-deoxo-6′-hydroxy-SRB1 to SRB1 in a time-dependent manner. Thus, these results clearly indicated that SrrO catalyzes the C-6′ oxidation at a final step in SRB biosynthesis.

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“…The starter moiety is then transferred to the first module of SbnO. Modules one and two of the assembly line then form the glutarimide moiety as previously described for the biosynthesis of Gladiofungin (44). Modules three to five elongate the nascent molecule according to the substrate specificity prediction for their KS domains.…”

Section: In Silico Analysis Of the Gene Cluster And Biosynthesis Hypomentioning

confidence: 99%

Sesbanimide R, a novel cytotoxic polyketide produced by magnetotactic bacteria

Awal

Haack

Bader

et al. 2020

Preprint

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Genomic information from various magnetotactic bacteria suggested that besides their common ability to form magnetosomes they potentially also represent a source of bioactive natural products. By using targeted deletion and transcriptional activation, we connected a large biosynthetic gene cluster (BGC) of the trans-AT PKS type to the biosynthesis of a novel polyketide in the alphaproteobacterium Magnetospirillum gryphiswaldense. Structure elucidation by mass spectrometry and NMR revealed that this secondary metabolite resembles sesbanimides which were very recently reported from other taxa. However, sesbanimide R exhibits an additional arginine moiety the presence of which reconciles inconsistencies in the previously proposed sesbanimide biosynthesis pathway when comparing the chemical structure and the potential biochemistry encoded in the BGC. In contrast to sesbanimides D, E and F, we were able to assign the stereocenter of the arginine moiety experimentally and two of the remaining three stereocenters by predictive biosynthetic tools. Sesbanimide R displayed strong cytotoxic activity against several carcinoma cell lines. ImportanceThe finding of this study contributes a new secondary metabolite member to the glutarimide-containing polyketides. The determined structure of sesbanimide R correlates with its cytotoxic bioactivity characteristic for members of this family. Sesbanimide R represents the first natural product isolated from magnetotactic bacteria and identifies this highly diverse group as a so far untapped source for the future discovery of novel secondary metabolites.

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Insect‐Associated Bacteria Assemble the Antifungal Butenolide Gladiofungin by Non‐Canonical Polyketide Chain Termination

Cited by 38 publications

References 43 publications

Identification of trans-AT polyketide clusters in two marine bacteria reveals cryptic similarities between distinct symbiosis factors

Identification of trans-AT polyketide clusters in two marine bacteria reveals cryptic similarities between distinct symbiosis factors

Functional Analysis of P450 Monooxygenase SrrO in the Biosynthesis of Butenolide-Type Signaling Molecules in Streptomyces rochei

Sesbanimide R, a novel cytotoxic polyketide produced by magnetotactic bacteria

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