Biology subjects

Dashti, Y.

Publications and source records attributed to Dashti, Y..

7 recordsLinked to original sources

bioRxiv2026

Hierarchical Cytochrome P450 Oxidations Program Persiathiacin Assembly

Thiopeptides are ribosomally synthesized and post-translationally modified peptides (RiPPs) that form complex bioactive scaffolds through extensive enzymatic tailoring. The polyglycosylated thiopeptides persiathiacins, exhibit potent activity against multidrug-resistant Mycobacterium tuberculosis (Mtb) and methicillin-resistant Staphylococcus aureus (MRSA). The persiathiacin biosynthetic gene cluster encodes six cytochrome P450 (CYP) enzymes, but the logic of their oxidative modifications was unknown. Here, we establish a protoplast-based genetic system for Actinokineospora and systematically assign functions to all P450s. We demonstrate that PerX hydroxylates the central thiazole, PerV installs the third indole-core crosslink required for macrocyclization, and PerT, not PerU, catalyses indole N-hydroxylation. Combined gene inactivation and metabolite profiling reveal a hierarchical enzymatic sequence leading to the mature scaffold prior to sugar installation. Notably, the intermediate accumulating in the{Omega} perX mutant exhibits enhanced anti-M. tuberculosis potency compared to persiathiacin A (IC50 = 0.07 vs 1.5 {micro}g mL-1). These results define the enzymatic logic and temporal organization of persiathiacin biosynthesis, providing a conceptual framework for rational diversification of complex thiopeptide natural products.

microbiology↗

bioRxiv2025

Discovery and Biosynthetic Origin of 4,4'-Dihydroxy-3,3',5,5' Tetrachlorobenzophenone Produced by the Clinical Isolate Burkholderia oklahomensis

Burkholderia oklahomensis LMG 23618T is a Burkholderia pseudomallei-like bacterium originally isolated in 1973 from a wound infection caused by a farming accident in Oklahoma. Metabolic profiling of an organic extract from cultures of B. oklahomensis LMG 23618T using UHPLC-ESI-Q-ToF-MS led to identification of three known metabolites, betulinan A, yersiniabactin and ulbactin B, in addition to a novel polycholorinated compound. Mass-directed purification enabled isolation of the novel specialized metabolite, which was shown by X-ray crystallography and NMR spectroscopic analysis to be 4,4'-dihydroxy-3,3',5,5'-tetrachlorobenzophenone. Feeding experiments with stable isotope-labelled precursors established that the carbon skeleton of this unusual metabolite derives from two molecules of tyrosine. This led us to propose a plausible biosynthetic pathway via decarboxylative condensation of 3, 5-dichloro-4-hydroxybenzoic acid with its coenzyme A thioester derivative. The absolute configuration of ulbactin B was also established as 4'R, 3''S, 7''S, 8''R using X-ray crystallography and NMR spectroscopy.

microbiology↗

bioRxiv2025

An O-acetylated derivative of piericidin A1 produced by Kitasatospora sp. A2-31 has potent activity against the cacao mirid bug, Helopeltis bakeri Poppius

There is an increasing demand for novel biopesticides to protect agricultural products and improve yields. To address this need, extracts from a library of Actinomycetes collected in the Philippines were evaluated against the cacao mirid bug, Helopeltis bakeri Poppius. Analysis of an active ethyl acetate extract from Kitasatospora sp. A2-31 led to the identification of a novel metabolite acetylpiericidin A1 (3) along with the known natural products piericidin A1 (1), piericidin A5 (2), chromomycin A2 (4), chromomycin A3 (5), and olivomycin A (6). Acetylpiericidin A1 demonstrated 100 % mortality against H. bakeri, while other metabolites exhibited either weak or no activity. Whole genome sequencing followed by bioinformatics analysis identified a gene downstream of the piericidin biosynthetic gene cluster that encodes a putative acetyltransferase proposed to catalyze acetylation of the C10 hydroxyl group of piericidin A1. The involvement of this gene in acetylpiericidin A1 biosynthesis was confirmed by (i) introducing an additional copy under the control of the ermE* promoter into Kitasatospora sp. A2-31, resulting in elevated production levels and (ii) through an in vitro enzymatic assay of the corresponding purified recombinant enzyme.

microbiology↗

bioRxiv2022

Mircubactin B rescues the lethal effect of cell wall biosynthesis mutations in Bacillus subtilis.

Growth of most rod-shaped bacteria is accompanied by the insertion of new peptidoglycan into the cylindrical cell wall. This insertion, which helps maintain and determine the shape of the cell, is guided by a complex protein machinery called the rod complex or elongasome. Although most of the proteins in this complex are essential under normal growth conditions, cell viability can be rescued, for reasons that are not understood, by the presence of a high (mM) Mg2+ concentration. We screened for natural product compounds that could rescue the growth of mutants affected in rod-complex function. By screening >2,000 extracts from a diverse collection of actinobacteria, we identified a new compound, mirubactin B, related to the known iron siderophore mirubactin A, which rescued growth in the low micromolar range, and this activity was confirmed by synthesising mirubactin B. The compound also displayed toxicity at higher concentrations, and this effect appears related to iron homeostasis. However, several lines of evidence suggest that the mirubactin B rescuing activity is not due simply to iron sequestration. The results demonstrate a novel antibacterial compound and add to growing evidence that bacterial siderophores have a range of activities beyond simple iron sequestration.

microbiology↗

bioRxiv2021

Discovery and Biosynthesis of Persiathiacins: Unusual Polyglycosylated Thiopeptides Active against Multi-drug resistant Tuberculosis

Thiopeptides are ribosomally biosynthesized and post-translationally modified peptides (RiPPs) that potently inhibit the growth of Gram-positive bacteria by targeting multiple steps in protein biosynthesis. The poor pharmacological properties of thiopeptides, in particular their low aqueous solubility, has hindered their development into clinically useful antibiotics. Antimicrobial activity screens of a library of Actinobacterial extracts led to discovery of the novel polyglycosylated thiopeptides persiathiacins A and B from Actinokineospora sp. UTMC 2475 and Actinokineospora sp. UTMC 2448. Persiathiacin A is active against methicillin-resistant Staphylococcus aureus (MRSA) and several Mycobacterium tuberculosis strains, including drug-resistant and multidrug-resistant clinical isolates, and does not significantly affect the growth of ovarian cancer cells at concentrations up to 400 M. In vitro translation assays showed that, like other thiopeptide antibiotics, persiathiacin A targets protein biosynthesis. Polyglycosylated thiopeptides are extremely rare and nothing is known about their biosynthesis. Sequencing and analysis of the Actinokineospora sp. UTMC 2448 genome enabled identification of the putative persiathiacin biosynthetic gene cluster. A cytochrome P450 encoded by this gene cluster catalyses the hydroxylation of nosiheptide in vitro and in vivo, consistent with the proposal that the cluster directs persiathiacin biosynthesis. Several genes in the cluster encode homologues of enzymes known to catalyse the assembly and attachment of deoxysugars during the biosynthesis of other classes of glycosylated natural products. The discovery of the persiathiacins and their biosynthetic gene cluster thus provides the basis for the development of biosynthetic engineering approaches to the creation of novel (poly)glycosylated thiopeptide derivatives with enhanced pharmacological properties.

microbiology↗

bioRxiv2020

Discovery and biosynthesis of gladiochelins: unusual lipodepsipeptide siderophores from Burkholderia gladioli

Burkholderia is a genus of diverse Gram-negative bacteria that includes several opportunistic pathogens. Siderophores, which transport iron from the environment into microbial cells, are important virulence factors in most pathogenic Burkholderia species. However, it is widely believed that Burkholderia gladioli, which can infect the lungs of cystic fibrosis (CF) sufferers, does not produce siderophores. B. gladioli BCC0238, isolated from the lung of a CF patient, produces two novel metabolites in a minimal medium containing glycerol and ribose as carbon sources. HPLC purification, followed by detailed spectroscopic analyses, identified these metabolites as unusual lipodepsipeptides containing a unique citrate-derived fatty acid and a rare dehydro-{beta}-alanine residue. The absolute configurations of the amino acid residues in the two metabolites was elucidated using Marfeys method and the gene cluster responsible for their biosynthesis was identified by bioinformatics and insertional mutagenesis. In-frame deletions and enzyme activity assays were used to investigate the functions of several proteins encoded by the biosynthetic gene cluster, which was found in the genomes of most B. gladioli isolates, suggesting that its metabolic products play an important role in the growth and/or survival of the species. The Chrome Azurol S (CAS) assay showed the metabolites bind ferric iron and that this supresses their production when added to the growth medium. Moreover, a gene encoding a TonB-dependent ferric-siderophore receptor is adjacent to the biosynthetic genes. Together, these observations suggest that these metabolites likely function as siderophores in B. gladioli.

microbiology↗

bioRxiv2020

Kill and cure: genomic phylogeny and bioactivity of a diverse collection of Burkholderia gladioli bacteria capable of pathogenic and beneficial lifestyles

Burkholderia gladioli is one of few bacteria with a broad ecology spanning disease in humans, animals, and plants, and encompassing beneficial interactions with multiple eukaryotic hosts. It is a plant pathogen, a bongkrekic acid toxin producing food-poisoning agent, and a lung pathogen in people with cystic fibrosis (CF). Contrasting beneficial traits include antifungal production exploited by insects to protect their eggs, plant protective abilities and antibiotic biosynthesis. We explored the ecological diversity and specialized metabolite biosynthesis of 206 B. gladioli strains, phylogenomically defining 5 evolutionary clades. Historical disease pathovars (pv) B. gladioli pv. allicola and B. gladioli pv. cocovenenans were phylogenetically distinct, while B. gladioli pv. gladioli and B. gladioli pv. agaricicola were indistinguishable. Soft-rot disease and CF infection pathogenicity traits were conserved across all pathovars. Biosynthetic gene clusters for toxoflavin, caryoynencin and enacyloxin were dispersed across B. gladioli, but bongkrekic acid and gladiolin production were clade specific. Strikingly, 13% of CF-infection strains characterised (n=194) were bongkrekic acid toxin positive, uniquely linking this food-poisoning risk factor to chronic lung disease. Toxin production was suppressed by exposing strains to the antibiotic trimethoprim, providing a potential therapeutic strategy to minimise poisoning risk in CF.

microbiology↗