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Frontiers in Microbiology 2022Heterologous expression is an indispensable approach to exploiting natural products from phylogenetically diverse microbial communities. In this study, we constructed a...
Heterologous expression is an indispensable approach to exploiting natural products from phylogenetically diverse microbial communities. In this study, we constructed a heterologous expression system based on strain E264 by deleting efflux pump genes and screening constitutive strong promoters. The biosynthetic gene cluster (BGC) of disorazol from So ce12 was expressed successfully with this host, and the yield of its product, disorazol F, rather than A, was improved to 38.3 mg/L by promoter substitution and insertion. In addition to the disorazol gene cluster, the BGC of rhizoxin from was also expressed efficiently, whereas no specific peak was detected when shuangdaolide BGC from sp. B59 was transformed into the host. This system provides another option to explore natural products from different phylogenetic taxa.
PubMed: 36466684
DOI: 10.3389/fmicb.2022.1073243 -
Access Microbiology 2023Several species of soil-dwelling nematodes are used in the biocontrol of crop pests, due to their natural capacity to kill diverse lepidopteran species. Although this...
Several species of soil-dwelling nematodes are used in the biocontrol of crop pests, due to their natural capacity to kill diverse lepidopteran species. Although this insect-killing trait is known to be augmented by the nematodes' endosymbionts, the role of other steinernematid-associated bacterial genera in the nematode lifecycle remains unclear. This genomic study aimed to determine the potential of to contribute to the entomopathogenicity of its host. Insect larvae were infected with three separate cultures. From each of the three treatments, the prevalent bacteria in the haemocoel of cadavers, four days post-infection, were isolated. These three bacterial isolates were morphologically characterised. DNA was extracted from each of the three bacterial isolates and used for long-read genome sequencing and assembly. Assemblies were used to delineate species and identify genes that encode insect toxins, antimicrobials, and confer antibiotic resistance. We assembled three complete genomes. Through digital DNA-DNA hybridisation analyses, we ascertained that the haemocoels of insect cadavers previously infected with sp. Kalro, sp. 75, and sp. 97 were dominated by Kalro, 75, and 97, respectively. Kalro and 97 formed a subspecies with other symbionts of steinernematids from Kenya. 75 phylogenetically clustered with pseudomonads that are characterised by high insecticidal activity. The 75 genome encoded the production pathway of insect toxins such as orfamides and rhizoxins, antifungals such as pyrrolnitrin and pyoluteorin, and the broad-spectrum antimicrobial 2,4-diacetylphloroglucinol. The 75 genome encoded resistance to over ten classes of antibiotics, including cationic lipopeptides. Steinernematid-associated bacteria hence have the biosynthetic potential to contribute to nematode entomopathogenicity.
PubMed: 37970093
DOI: 10.1099/acmi.0.000659.v3 -
Microbial Ecology May 2019This work reports the comparison of the genome sequence and the ability to inhibit fungal growth of two Pseudomonas protegens related strains that were isolated from the...
This work reports the comparison of the genome sequence and the ability to inhibit fungal growth of two Pseudomonas protegens related strains that were isolated from the same hydroponic culture of lamb's lettuce. The two strains were very similar in their core genome but one strain, Pf4, contained three gene clusters for the production of secondary metabolites, i.e., pyoluteorin (plt), pyrrolnitrin (prn), and rhizoxin (rzx), that were missing in the other strain, Pf11. The difference between the two strains was not due to simple insertion events, but to a relatively complex differentiation focused on the accessory genomes. In dual culture assays, both strains inhibited nearly all tested fungal strains, yet Pf4 exerted a significantly stronger fungal growth inhibition than Pf11. In addition to the differences in the secondary metabolite production associated genes abundance, the genome of Pf4 was more stable, smaller in size and with a lower number of transposons. The preservation of a dynamic equilibrium within natural populations of different strains comprised in the same species but differing in their secondary metabolite repertoire and in their genome stability may be functional to the adaptation to environmental changes.
Topics: Antifungal Agents; Genome, Bacterial; Hydroponics; Pseudomonas; Pythium; Rhizoctonia
PubMed: 30088023
DOI: 10.1007/s00248-018-1238-5 -
Current Medicinal Chemistry 2020Microtubule Targeting Agents (MTAs) represent the most successful anticancer drugs for cancer chemotherapy. Through interfering with the tubulin polymerization and...
BACKGROUND
Microtubule Targeting Agents (MTAs) represent the most successful anticancer drugs for cancer chemotherapy. Through interfering with the tubulin polymerization and depolymerization dynamics, MTAs influence intracellular transport and cell signal pathways, inhibit cell mitosis and cell proliferation, and induce cell apoptosis and death. The tubulin maytansine site binding agents are natural or nature-derived products that represent one type of the MTAs that inhibit tubulin polymerization and exhibit potent antitumor activity both in vitro and in vivo. They are used as Antibody-Drug Conjugates (ADCs) in cancer chemotherapy.
METHODS
Using SciFinder® as a tool, the publications about maytansine, its derivatives, maytansine binding site, maytansine site binding agents and their applications as MTAs for cancer therapy were surveyed with an exclusion on those published as patents. The latest progresses in clinical trials were obtained from the clinical trial web.
RESULTS
This article presents an introduction about MTAs, maytansine, maytansine binding site and its ligands, the applications of these ligands as MTAs and ADCs in cancer therapy.
CONCLUSION
The maytansine site binding agents are powerful MTAs for cancer chemotherapy. The maytansine site ligands-based ADCs are used in clinic or under clinical trials as cancer targeted therapy to improve their selectivity and to reduce their side effects. Further improvements in the delivery efficiency of the ADCs will benefit the patients in cancer targeted therapy.
Topics: Antineoplastic Agents; Humans; Immunoconjugates; Ligands; Maytansine; Microtubules; Neoplasms; Trastuzumab; Tubulin
PubMed: 32175831
DOI: 10.2174/0929867327666200316144610 -
Applied and Environmental Microbiology Dec 2015Pseudomonas protegens strain Pf-5 is a rhizosphere bacterium that suppresses soilborne plant diseases and produces at least seven different secondary metabolites with...
An Interspecies Signaling System Mediated by Fusaric Acid Has Parallel Effects on Antifungal Metabolite Production by Pseudomonas protegens Strain Pf-5 and Antibiosis of Fusarium spp.
Pseudomonas protegens strain Pf-5 is a rhizosphere bacterium that suppresses soilborne plant diseases and produces at least seven different secondary metabolites with antifungal properties. We derived mutants of Pf-5 with single and multiple mutations in biosynthesis genes for seven antifungal metabolites: 2,4-diacetylphoroglucinol (DAPG), pyrrolnitrin, pyoluteorin, hydrogen cyanide, rhizoxin, orfamide A, and toxoflavin. These mutants were tested for inhibition of the pathogens Fusarium verticillioides and Fusarium oxysporum f. sp. pisi. Rhizoxin, pyrrolnitrin, and DAPG were found to be primarily responsible for fungal antagonism by Pf-5. Previously, other workers showed that the mycotoxin fusaric acid, which is produced by many Fusarium species, including F. verticillioides, inhibited the production of DAPG by Pseudomonas spp. In this study, amendment of culture media with fusaric acid decreased DAPG production, increased pyoluteorin production, and had no consistent influence on pyrrolnitrin or orfamide A production by Pf-5. Fusaric acid also altered the transcription of biosynthetic genes, indicating that the mycotoxin influenced antibiotic production by Pf-5 at the transcriptional level. Addition of fusaric acid to the culture medium reduced antibiosis of F. verticillioides by Pf-5 and derivative strains that produce DAPG but had no effect on antibiosis by Pf-5 derivatives that suppressed F. verticillioides due to pyrrolnitrin or rhizoxin production. Our results demonstrated the importance of three compounds, rhizoxin, pyrrolnitrin, and DAPG, in suppression of Fusarium spp. by Pf-5 and confirmed that an interspecies signaling system mediated by fusaric acid had parallel effects on antifungal metabolite production and antibiosis by the bacterial biological control organism.
Topics: Antibiosis; Antifungal Agents; Culture Media; Fusaric Acid; Fusarium; Metabolic Networks and Pathways; Microbial Interactions; Pseudomonas; Signal Transduction; Transcription, Genetic
PubMed: 26655755
DOI: 10.1128/AEM.02574-15 -
ELife Sep 2014Some of the proteins and enzymes that allow bacteria to enter living fungal cells and cause rice seedling blight have been identified.
Some of the proteins and enzymes that allow bacteria to enter living fungal cells and cause rice seedling blight have been identified.
Topics: Burkholderia; Macrolides; Rhizopus; Symbiosis
PubMed: 25268072
DOI: 10.7554/eLife.04603 -
Microbiology Resource Announcements Aug 2018Here, we present the draft genome sequence of Pseudomonas protegens strain BNJ-SS-45, which was isolated from wheat rhizosphere. The genome is assembled with...
Here, we present the draft genome sequence of Pseudomonas protegens strain BNJ-SS-45, which was isolated from wheat rhizosphere. The genome is assembled with 7,116,445 bp with a GC content of 63.34% consisting of 32 scaffolds. The genome is useful in prediction of secondary metabolites, particularly rhizoxin, pyoverdine, and bacteriocin.
PubMed: 30533914
DOI: 10.1128/MRA.00926-18 -
Nature Chemical Biology Dec 2015Biosynthesis of rhizoxin in Burkholderia rhizoxinica affords an unusual polyketide synthase module with ketosynthase and branching domains that install the δ-lactone,...
Biosynthesis of rhizoxin in Burkholderia rhizoxinica affords an unusual polyketide synthase module with ketosynthase and branching domains that install the δ-lactone, conferring antimitotic activity. To investigate their functions in chain branching, we designed chimeric modules with structurally similar domains from a glutarimide-forming module and a dehydratase. Biochemical, kinetic and mutational analyses reveal a structural role of the accessory domains and multifarious catalytic actions of the ketosynthase.
Topics: Acyltransferases; Burkholderia; Macrolides; Molecular Conformation; Polyketide Synthases; Polyketides
PubMed: 26479442
DOI: 10.1038/nchembio.1932 -
EFSA Journal. European Food Safety... Oct 2020The European Commission requested EFSA to provide scientific advice on the translocation potential by MA342 in plants after seed treatment of cereals and peas and, if...
The European Commission requested EFSA to provide scientific advice on the translocation potential by MA342 in plants after seed treatment of cereals and peas and, if applicable, for a revision of the assessment of the risk to humans by its metabolite 2,3-deepoxy-2,3-didehydro-rhizoxin (DDR) and this based on the evidence available in the dossier for renewal of the approval. The information from other strains than MA342 was taken into account with care, because the studies available in the dossier did not confirm the identity of the strain MA342 as belonging to the species . It has been concluded that there is a potential for translocation of MA342 to edible plant parts following seed treatment till an estimated concentration up to about 10 cfu/g and some exposure can be assumed by consumption of fresh commodities. Also, production of the metabolite DDR in the plant cannot be excluded. Regarding levels of DDR in the raw agricultural commodities, exposure estimates based on the limit of quantification (LOQ) for DDR in cereals cannot be further refined while there is no information on the levels of DDR in peas in the dossier. As regards genotoxicity, DDR induced chromosomal damage; however, it was not possible to conclude whether it is through an aneugenic or clastogenic mechanism. Hence, it is not possible to draw a reliable conclusion that DDR is producing an aneugenic effect nor to determine a threshold dose for aneugenicity. Thus, it is not possible to revise the human risk assessment as regards exposure to DDR. The concerns identified in the EFSA conclusion of 2017 remain.
PubMed: 33133274
DOI: 10.2903/j.efsa.2020.6276 -
Angewandte Chemie (International Ed. in... Oct 2014Polyketides typically result from head-to-tail condensation of acyl thioesters to produce highly functionalized linear chains. The biosynthesis of the phytotoxin...
Polyketides typically result from head-to-tail condensation of acyl thioesters to produce highly functionalized linear chains. The biosynthesis of the phytotoxin rhizoxin, however, involves a polyketide synthase (PKS) module that introduces a δ-lactone chain branch through Michael addition of a malonyl extender to an α,β-unsaturated intermediate unit. To evaluate the scope of the branching module, polyketide mimics were synthesized and their biotransformation by the reconstituted PKS module from the Rhizopus symbiont Burkholderia rhizoxinica was monitored in vitro. The impact of the type and configuration of the δ-substituents was probed and it was found that amino-substituted surrogates yield the corresponding lactams. A carboxamide analogue was transformed into a glutarimide unit, which can be found in many natural products. Our findings illuminate the biosynthesis of glutarimide-bearing polyketides and also demonstrate the utility of this branching module for synthetic biology.
Topics: Heterocyclic Compounds; Lactams; Lactones; Piperidones; Polyketide Synthases; Polyketides
PubMed: 25214315
DOI: 10.1002/anie.201407282