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Cell Chemical Biology Aug 2023Darobactins represent a class of ribosomally synthesized and post-translationally modified peptide (RiPP) antibiotics featuring a rare bicyclic structure. They target...
Darobactins represent a class of ribosomally synthesized and post-translationally modified peptide (RiPP) antibiotics featuring a rare bicyclic structure. They target the Bam-complex of Gram-negative bacteria and exhibit in vivo activity against drug-resistant pathogens. First isolated from Photorhabdus species, the corresponding biosynthetic gene clusters (BGCs) are widespread among γ-proteobacteria, including the genera Vibrio, Yersinia, and Pseudoalteromonas (P.). While the organization of the BGC core is highly conserved, a small subset of Pseudoalteromonas carries an extended BGC with additional genes. Here, we report the identification of brominated and dehydrated darobactin derivatives from P. luteoviolacea strains. The marine derivatives are active against multidrug-resistant (MDR) Gram-negative bacteria and showed solubility and plasma protein binding ability different from darobactin A, rendering it more active than darobactin A. The halogenation reaction is catalyzed by DarH, a new class of flavin-dependent halogenases with a novel fold.
Topics: Phenylpropionates; Gram-Negative Bacteria; Metabolome
PubMed: 37451267
DOI: 10.1016/j.chembiol.2023.06.011 -
Bio-protocol Jul 2023The easyPACId (easy Promoter Activation and Compound Identification) approach is focused on the targeted activation of natural product biosynthetic gene clusters (BGCs)...
The easyPACId (easy Promoter Activation and Compound Identification) approach is focused on the targeted activation of natural product biosynthetic gene clusters (BGCs) encoding non-ribosomal peptide synthetases (NRPS), polyketide synthases (PKS), NRPS-PKS hybrids, or other BGC classes. It was applied to entomopathogenic bacteria of the genera Xenorhabdus and Photorhabdus by exchanging the natural promoter of desired BGCs against the L-arabinose inducible PBAD promoter in ∆hfq mutants of the respective strains. The crude (culture) extracts of the cultivated easyPACId mutants are enriched with the single compound or compound class and can be tested directly against various target organisms without further purification of the produced natural products. Furthermore, isolation and identification of compounds from these mutants is simplified due to the reduced background in the ∆hfq strains. The approach avoids problems often encountered in heterologous expression hosts, chemical synthesis, or tedious extraction of desired compounds from wild-type crude extracts. This protocol describes easyPACId for Xenorhabdus and Photorhabdus, but it was also successfully adapted to Pseudomonas entomophila and might be suitable for other proteobacteria that carry hfq.
PubMed: 37449040
DOI: 10.21769/BioProtoc.4709 -
Plant Disease Nov 2023Root-knot nematodes (RKNs) cause significant economic damage to crop plants, spurring demand for safe, affordable, and sustainable nematicides. A previous study by our...
Root-knot nematodes (RKNs) cause significant economic damage to crop plants, spurring demand for safe, affordable, and sustainable nematicides. A previous study by our research team showed that the combination of two nematicidal secondary metabolites (SMs) derived from bacteria, -cinnamic acid (-CA), and (4)-5-phenylpent-4-enoic acid (PPA) have a synergistic effect against RKNs in vitro. In this study, we considered in planta assays to assess the effects of this SM mixture on the virulence and reproductive fitness of the RKN in a cowpea. Factorial combinations of five -CA + PPA concentrations (0, 9.0, 22.9, 57.8, and 91.0 μg/ml) and two nematode inoculation conditions (presence or absence) were evaluated in 6-week growth chamber experiments. Results from this study showed that a single root application of the -CA + PPA mixture significantly reduced the penetration of infective juveniles (J2s) into the cowpea roots. The potential toxicity of -CA + PPA on RKN-susceptible cowpea seedlings was also investigated. The effect of -CA + PPA × nematode inoculation interactions and the -CA + PPA mixture did not show significant phytotoxic effects, nor did it adversely affect plant growth parameters or alter leaf chlorophyll content. Total leaf chlorophyll and chlorophyll content were significantly reduced (by 15 and 22%, respectively) only by the nematode inoculum and not by any of the SM treatments. Our results suggest that a single root application of a mixture of -CA and PPA reduces J2's ability to infect the roots without impairing plant growth or chlorophyll content.
Topics: Animals; Tylenchoidea; Vigna; Photorhabdus; Antinematodal Agents; Chlorophyll
PubMed: 37330631
DOI: 10.1094/PDIS-11-22-2574-SC -
Research in Microbiology 2023The Resistance-nodulation-division (RND)-type AcrAB-TolC efflux pump contributes to multidrug resistance in Gram-negative bacteria. Recently, the bacterium Photorhabdus...
The Resistance-nodulation-division (RND)-type AcrAB-TolC efflux pump contributes to multidrug resistance in Gram-negative bacteria. Recently, the bacterium Photorhabdus laumondii TT01 has emerged as a goldmine for novel anti-infective drug discovery. Outside plants, Photorhabdus is the only Gram-negative known to produce stilbene-derivatives including 3,5-dihydroxy-4-ethyl-trans-stilbene and 3,5-dihydroxy-4-isopropyl-trans-stilbene (IPS). IPS is a bioactive polyketide which received considerable attention, mainly because of its antimicrobial properties, and is currently in late-stage clinical development as a topical treatment for psoriasis and dermatitis. To date, little is known about how Photorhabdus survives in the presence of stilbenes. We combined genetic and biochemical approaches to assess whether AcrAB efflux pump exports stilbenes in P. laumondii. We demonstrated that the wild-type (WT) exerts an antagonistic activity against its derivative ΔacrA mutant, and that is able to outcompete it in a dual-strain co-culture assay. The ΔacrA mutant also showed high sensitivity to 3,5-dihydroxy-4-ethyl-trans-stilbene and IPS as well as decreased IPS concentrations in its supernatant comparing to the WT. We report here a mechanism of self-resistance against stilbene derivatives of P. laumondii TT01, which enables these bacteria to survive under high concentrations of stilbenes by extruding them out via the AcrAB efflux pump.
PubMed: 37196776
DOI: 10.1016/j.resmic.2023.104081