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Chembiochem : a European Journal of... Oct 2011Chain armor against tumor cells: The oxazole side chain in the antimitotic agent rhizoxin S2 (1) was successfully replaced through mutasynthesis by using an engineered...
Chain armor against tumor cells: The oxazole side chain in the antimitotic agent rhizoxin S2 (1) was successfully replaced through mutasynthesis by using an engineered mutant impaired in heterocyclization. Incorporation of 12 non-natural surrogates into fully processed rhizoxin analogues revealed a remarkable substrate flexibility of the PKS-NRPS hybrid.
Topics: Amino Acid Sequence; Antibiotics, Antineoplastic; Burkholderia; Genes, Fungal; Genetic Loci; Macrolides; Molecular Sequence Data; Mutation; Oxazoles; Peptide Synthases; Polyketide Synthases
PubMed: 23106078
DOI: 10.1002/cbic.201100387 -
Angewandte Chemie (International Ed. in... Sep 2012
Topics: Chromatography, High Pressure Liquid; Macrolides; Molecular Structure; Rhizopus
PubMed: 22915379
DOI: 10.1002/anie.201204540 -
Organic & Biomolecular Chemistry Aug 2012Through metabolic profiling of mutants and wild type of the endofungal bacterium Burkholderia rhizoxinica two novel rhizoxin derivatives with unusual nitrile...
Through metabolic profiling of mutants and wild type of the endofungal bacterium Burkholderia rhizoxinica two novel rhizoxin derivatives with unusual nitrile substitutions were discovered. The nitrile groups result from a photochemical oxidative cleavage of the oxazolyl moiety. In vitro studies revealed that the photooxidation by singlet oxygen also takes place in the absence of a photosensitizer, and that also a thiazolyl-substituted rhizoxin analogue undergoes the same transformation. The resulting nitriles have antimitotic properties but are significantly less active than the parent compounds. These results highlight the impact of photoreactions onto the antiproliferative agent and encourage the introduction of bioisosteric groups that render the compound less susceptible towards photooxidation.
Topics: Antimitotic Agents; Cell Line, Tumor; Humans; Macrolides; Nitriles; Oxazoles; Photochemical Processes
PubMed: 22453231
DOI: 10.1039/c2ob25250c -
ChemMedChem Nov 2011
Topics: Amides; Antineoplastic Agents; Cell Line, Tumor; Drug Screening Assays, Antitumor; HeLa Cells; Human Umbilical Vein Endothelial Cells; Humans; Macrolides; Structure-Activity Relationship
PubMed: 21990089
DOI: 10.1002/cmdc.201100319 -
PLoS Pathogens Jun 2011
Topics: Burkholderia; Crops, Agricultural; Drug Design; Food Safety; Humans; Macrolides; Plants; Rhizopus; Symbiosis; Zygomycosis
PubMed: 21738468
DOI: 10.1371/journal.ppat.1002096 -
BMC Genomics May 2011Burkholderia rhizoxinica is an intracellular symbiont of the phytopathogenic zygomycete Rhizopus microsporus, the causative agent of rice seedling blight. The...
BACKGROUND
Burkholderia rhizoxinica is an intracellular symbiont of the phytopathogenic zygomycete Rhizopus microsporus, the causative agent of rice seedling blight. The endosymbiont produces the antimitotic macrolide rhizoxin for its host. It is vertically transmitted within vegetative spores and is essential for spore formation of the fungus. To shed light on the evolution and genetic potential of this model organism, we analysed the whole genome of B. rhizoxinica HKI 0454 - a type strain of endofungal Burkholderia species.
RESULTS
The genome consists of a structurally conserved chromosome and two plasmids. Compared to free-living Burkholderia species, the genome is smaller in size and harbors less transcriptional regulator genes. Instead, we observed accumulation of transposons over the genome. Prediction of primary metabolic pathways and transporters suggests that endosymbionts consume host metabolites like citrate, but might deliver some amino acids and cofactors to the host. The rhizoxin biosynthesis gene cluster shows evolutionary traces of horizontal gene transfer. Furthermore, we analysed gene clusters coding for nonribosomal peptide synthetases (NRPS). Notably, B. rhizoxinica lacks common genes which are dedicated to quorum sensing systems, but is equipped with a large number of virulence-related factors and putative type III effectors.
CONCLUSIONS
B. rhizoxinica is the first endofungal bacterium, whose genome has been sequenced. Here, we present models of evolution, metabolism and tools for host-symbiont interaction of the endofungal bacterium deduced from whole genome analyses. Genome size and structure suggest that B. rhizoxinica is in an early phase of adaptation to the intracellular lifestyle (genome in transition). By analysis of tranporters and metabolic pathways we predict how metabolites might be exchanged between the symbiont and its host. Gene clusters for biosynthesis of secondary metabolites represent novel targets for genomic mining of cryptic natural products. In silico analyses of virulence-associated genes, secreted proteins and effectors might inspire future studies on molecular mechanisms underlying bacterial-fungal interaction.
Topics: Anti-Bacterial Agents; Bacterial Proteins; Biological Transport; Burkholderia; Drug Resistance, Bacterial; Drug Resistance, Multiple; Evolution, Molecular; Fimbriae, Bacterial; Genome, Bacterial; Genomics; Lipopolysaccharides; Pseudogenes; Rhizopus; Symbiosis
PubMed: 21539752
DOI: 10.1186/1471-2164-12-210 -
Journal of Bacteriology Feb 2011Burkholderia rhizoxinica is an intracellular symbiont of the phytopathogenic fungus Rhizopus microsporus. The vertically transmitted endosymbiont not only delivers the...
Burkholderia rhizoxinica is an intracellular symbiont of the phytopathogenic fungus Rhizopus microsporus. The vertically transmitted endosymbiont not only delivers the antimitotic macrolide rhizoxin to its host but is also essential for vegetative spore formation of the fungus. To shed light on the genetic equipment of this model organism, we sequenced the whole genome of B. rhizoxinica HKI 0454, thus providing the first genomic insight into an intracellular mutualist of a fungal species. The 3.75-Mb genome consists of a chromosome and two strain-specific plasmids. The primary metabolism appears to be specialized for the uptake of fungal metabolites. Besides the rhizoxin biosynthesis gene cluster, there are 14 loci coding for nonribosomal peptide synthetase (NRPS) assembly lines, which represent novel targets for genomic mining of cryptic natural products. Furthermore, the endosymbionts are equipped with a repertoire of virulence-related factors, which can now be studied to elucidate molecular mechanisms underlying bacterial-fungal interaction.
Topics: Burkholderia; Chromosomes, Bacterial; DNA, Bacterial; Genome, Bacterial; Molecular Sequence Data; Plasmids; Sequence Analysis, DNA
PubMed: 21131495
DOI: 10.1128/JB.01318-10 -
The ISME Journal Feb 2011Burkholderia rhizoxinica and Rhizopus microsporus form a unique symbiosis in which intracellular bacteria produce the virulence factor of the phytopathogenic fungus....
Burkholderia rhizoxinica and Rhizopus microsporus form a unique symbiosis in which intracellular bacteria produce the virulence factor of the phytopathogenic fungus. Notably, the host strictly requires endobacteria to sporulate. In this study, we show that the endofungal bacteria possess a type III secretion system (T3SS), which has a crucial role in the maintenance of the alliance. Mutants defective in type III secretion show reduced intracellular survival and fail to elicit sporulation of the host. Furthermore, genes coding for T3SS components are upregulated during cocultivation of the bacterial symbiont with their host. This is the first report on a T3SS involved in bacterial-fungal symbiosis. Phylogenetic analysis revealed that the T3SS represents a prototype of a clade of yet uncharacterized T3SSs within the hrp superfamily of T3SSs from plant pathogenic microorganisms. In a control experiment, we demonstrate that under laboratory conditions, rhizoxin production was not required for establishment of the symbiotic interaction.
Topics: Bacterial Secretion Systems; Burkholderia; Gene Expression Regulation, Bacterial; Molecular Sequence Annotation; Molecular Sequence Data; Multigene Family; Mutation; Phylogeny; Plants; Rhizopus; Symbiosis; Virulence Factors
PubMed: 20720578
DOI: 10.1038/ismej.2010.126 -
Angewandte Chemie (International Ed. in... Feb 2010
Topics: Chemistry, Pharmaceutical; Macrolides; Models, Biological; Molecular Structure
PubMed: 20033973
DOI: 10.1002/anie.200905467 -
International Journal of Food... Jan 2010Mould fungi are not only well known for food spoilage through toxin formation but also for the production of fermented foods. In Asian countries, the fermentation of soy...
Mould fungi are not only well known for food spoilage through toxin formation but also for the production of fermented foods. In Asian countries, the fermentation of soy beans and tofu for tempe and sufu production with various Rhizopus strains is widespread. Here we report the finding of toxinogenic bacteria in a starter culture used for sufu production. By means of metabolic profiling of the fungus under standard conditions for tempe and sufu production, we found that toxins of the rhizoxin complex are produced in critical amounts. Considering that rhizoxins are severe toxins with strong antimitotic activity it is important to notice that our findings uncover a health-threatening symbiosis in food processing. A simple PCR method for detecting toxinogenic endofungal bacteria in starter cultures is proposed.
Topics: Burkholderia; Fermentation; Food Microbiology; Macrolides; Mycotoxins; Rhizopus; Glycine max; Symbiosis
PubMed: 19942312
DOI: 10.1016/j.ijfoodmicro.2009.10.010