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Pathogens (Basel, Switzerland) Mar 2023Symbiotic bacteria form a mutualistic relationship with nematodes and are pathogenic to many insect pests. They kill insects using various strategies to evade or...
Symbiotic bacteria form a mutualistic relationship with nematodes and are pathogenic to many insect pests. They kill insects using various strategies to evade or suppress their humoral and cellular immunity. Here we evaluate the toxic effects of these bacteria and their secondary metabolites on the survival and phenoloxidase (PO) activation of larvae using biochemical and molecular methods. The results show H06 and All treatments caused significant reductions in the number of larvae in a dose-dependent manner. Secondly, the immune system recognizes symbiotic bacteria at early and late stages of infection via the induction of C-type lectin. Live symbiotic bacteria significantly inhibit PO activity in whereas heat-treated bacteria strongly increase PO activity. Additionally, expression levels of four proPhenoloxidase genes following treatment with H06 and All were compared. We found that the expression levels of all proPhenoloxidase genes were significantly down-regulated at all-time points. Similarly, treatments of larvae with metabolites benzylideneacetone and oxindole significantly down-regulated the expression of the PPO gene and inhibited PO activity. However, the addition of arachidonic acid to metabolite-treated larvae restored the expression level of the PPO gene and increased PO activity. Our results provide new insight into the roles of symbiotic bacteria in countering the insect phenoloxidase activation system.
PubMed: 37111392
DOI: 10.3390/pathogens12040506 -
Frontiers in Insect Science 2023The term "microbial control" has been used to describe the use of microbial pathogens (bacteria, viruses, or fungi) or entomopathogenic nematodes (EPNs) to control... (Review)
Review
The term "microbial control" has been used to describe the use of microbial pathogens (bacteria, viruses, or fungi) or entomopathogenic nematodes (EPNs) to control various insect pest populations. EPNs are among the best biocontrol agents, and major developments in their use have occurred in recent decades, with many surveys having been conducted all over the world to identify EPNs that may have potential in the management of insect pests. For nematodes, the term "entomopathogenic" means "causing disease to insects" and is mainly used in reference to the bacterial symbionts of and ( and , respectively), which cause EPN infectivity. A compendium of our multiannual experiences on EPN surveys and on their collection, identification, characterization, and use in agro-forestry ecosystems is presented here to testify and demonstrate once again that biological control with EPNs is possible and offers many advantages over chemicals, such as end-user safety, minimal damage to natural enemies, and lack of environmental pollution, which are essential conditions for an advanced IPM strategy.
PubMed: 38469514
DOI: 10.3389/finsc.2023.1195254 -
Parasites & Vectors Jul 2020The control of insects of medical importance, such as Aedes aegypti and Aedes albopictus are still the only effective way to prevent the transmission of diseases, such... (Review)
Review
The control of insects of medical importance, such as Aedes aegypti and Aedes albopictus are still the only effective way to prevent the transmission of diseases, such as dengue, chikungunya and Zika. Their control is performed mainly using chemical products; however, they often have low specificity to non-target organisms, including humans. Also, studies have reported resistance to the most commonly used insecticides, such as the organophosphate and pyrethroids. Biological control is an ecological and sustainable method since it has a slow rate of insect resistance development. Bacterial species of the genera Xenorhabdus and Photorhabdus have been the target of several research groups worldwide, aiming at their use in agricultural, pharmaceutical and industrial products. This review highlights articles referring to the use of Xenorhabdus and Photorhabdus for insects and especially for mosquito control proposing future ways for their biotechnological applicability. Approximately 24 species of Xenorhabdus and five species of Photorhabdus have been described to have insecticidal properties. These studies have shown genes that are capable of encoding low molecular weight proteins, secondary toxin complexes and metabolites with insecticide activities, as well as antibiotic, fungicidal and antiparasitic molecules. In addition, several species of Xenorhabdus and Photorhabdus showed insecticidal properties against mosquitoes. Therefore, these biological agents can be used in new control methods, and must be, urgently considered in short term, in studies and applications, especially in mosquito control.
Topics: Aedes; Animals; Bacterial Toxins; Chikungunya Fever; Dengue; Genes, Bacterial; Insecta; Insecticides; Larva; Mosquito Control; Mosquito Vectors; Pest Control, Biological; Photorhabdus; Vector Borne Diseases; Xenorhabdus; Zika Virus Infection
PubMed: 32727530
DOI: 10.1186/s13071-020-04236-6 -
Nature Communications Jun 2020Toxin complex (Tc) toxins are virulence factors of pathogenic bacteria. Tcs are composed of three subunits: TcA, TcB and TcC. TcA facilitates receptor-toxin interaction...
Toxin complex (Tc) toxins are virulence factors of pathogenic bacteria. Tcs are composed of three subunits: TcA, TcB and TcC. TcA facilitates receptor-toxin interaction and membrane permeation, TcB and TcC form a toxin-encapsulating cocoon. While the mechanisms of holotoxin assembly and pore formation have been described, little is known about receptor binding of TcAs. Here, we identify heparins/heparan sulfates and Lewis antigens as receptors for different TcAs from insect and human pathogens. Glycan array screening reveals that all tested TcAs bind negatively charged heparins. Cryo-EM structures of Morganella morganii TcdA4 and Xenorhabdus nematophila XptA1 reveal that heparins/heparan sulfates unexpectedly bind to different regions of the shell domain, including receptor-binding domains. In addition, Photorhabdus luminescens TcdA1 binds to Lewis antigens with micromolar affinity. Here, the glycan interacts with the receptor-binding domain D of the toxin. Our results suggest a glycan dependent association mechanism of Tc toxins on the host cell surface.
Topics: Animals; Bacterial Toxins; Binding Sites; Cell Adhesion; Cell Membrane; HEK293 Cells; Heparin; Humans; Insecta; Lewis X Antigen; Models, Molecular; Molecular Docking Simulation; Morganella morganii; Photorhabdus; Polysaccharides; Xenorhabdus
PubMed: 32483155
DOI: 10.1038/s41467-020-16536-7 -
Plants (Basel, Switzerland) Aug 2021The current approaches to sustainable agricultural development aspire to use safer means to control pests and pathogens. bacteria that are insecticidal symbionts of... (Review)
Review
The current approaches to sustainable agricultural development aspire to use safer means to control pests and pathogens. bacteria that are insecticidal symbionts of entomopathogenic nematodes in the genus can provide such a service with a treasure trove of insecticidal compounds and an ability to cope with the insect immune system. This review highlights the need of -derived insecticidal, fungicidal, pharmaceutical, parasiticidal, antimicrobial, and toxic materials to fit into current, or emerging, holistic strategies, mainly for managing plant pests and pathogens. The widespread use of these bacteria, however, has been slow, due to cost, natural presence within the uneven distribution of their nematode partners, and problems with trait stability during in vitro culture. Yet, progress has been made, showing an ability to overcome these obstacles via offering affordable mass production and mastered genome sequencing, while detecting more of their beneficial bacterial species/strains. Their high pathogenicity to a wide range of arthropods, efficiency against diseases, and versatility, suggest future promising industrial products. The many useful properties of these bacteria can facilitate their integration with other pest/disease management tactics for crop protection.
PubMed: 34451705
DOI: 10.3390/plants10081660 -
Experimental Parasitology Sep 2019Only two drugs are currently available for the treatment of Chagas disease and their effectiveness are unsatisfactory. Photorhabdus luminescens and Xenorhabdus...
Only two drugs are currently available for the treatment of Chagas disease and their effectiveness are unsatisfactory. Photorhabdus luminescens and Xenorhabdus nematophila, two enteric bacteria highly pathogenic to a broad range of insects, have been studied as potential source for bioactive metabolites against protozoa causing neglected tropical diseases. Therefore, we tested the in vitro anti-Trypanosoma cruzi activity of secreted metabolites from these bacteria. The conditioned medium of X. nematophila and P. luminescens showed significant parasiticidal activity in a concentration-dependent manner (ICXN = 0.34 mg/mL, ICPL = 1.0 mg/mL). The parasiticidal compound was identified as a small molecule stable to heating and pH changes ranging from 2 to 12. Moreover, anti-Trypanosoma molecules secreted by both bacteria stimulate the trypanocidal activity of macrophages by a mechanism independent of nitric oxide. Summarizing, our studies reveal that P. luminescens and X. nematophila are potential sources of putative novel drugs against Chagas disease.
Topics: Analysis of Variance; Animals; Bacterial Proteins; Biological Assay; Chagas Disease; Culture Media, Conditioned; Endopeptidase K; Humans; Hydrogen-Ion Concentration; Inhibitory Concentration 50; Photorhabdus; Temperature; Trypanocidal Agents; Trypanosoma cruzi; Xenorhabdus
PubMed: 31279930
DOI: 10.1016/j.exppara.2019.107724 -
International Journal of Molecular... Jun 2022Due to its essential role in cellular processes, actin is a common target for bacterial toxins. One such toxin, TccC3, is an effector domain of the ABC-toxin produced by...
Due to its essential role in cellular processes, actin is a common target for bacterial toxins. One such toxin, TccC3, is an effector domain of the ABC-toxin produced by entomopathogenic bacteria of spp. Unlike other actin-targeting toxins, TccC3 uniquely ADP-ribosylates actin at Thr-148, resulting in the formation of actin aggregates and inhibition of phagocytosis. It has been shown that the fully modified F-actin is resistant to depolymerization by cofilin and gelsolin, but their effects on partially modified actin were not explored. We found that only F-actin unprotected by tropomyosin is the physiological TccC3 substrate. Yet, ADP-ribosylated G-actin can be produced upon cofilin-accelerated F-actin depolymerization, which was only mildly inhibited in partially modified actin. The affinity of TccC3-ADP-ribosylated G-actin for profilin and thymosin-β4 was weakened moderately but sufficiently to potentiate spontaneous polymerization in their presence. Interestingly, the Arp2/3-mediated nucleation was also potentiated by T148-ADP-ribosylation. Notably, even partially modified actin showed reduced bundling by plastins and α-actinin. In agreement with the role of these and other tandem calponin-homology domain actin organizers in the assembly of the cortical actin network, TccC3 induced intense membrane blebbing in cultured cells. Overall, our data suggest that TccC3 imposes a complex action on the cytoskeleton by affecting F-actin nucleation, recycling, and interaction with actin-binding proteins involved in the integration of actin filaments with each other and cellular elements.
Topics: ADP Ribose Transferases; Actin Cytoskeleton; Actin Depolymerizing Factors; Actins; Adenosine Diphosphate; Photorhabdus
PubMed: 35806028
DOI: 10.3390/ijms23137026 -
Structure (London, England : 1993) May 2023Modification of the polyketide anthraquinone AQ-256 in the entomopathogenic Photorhabdus luminescens involves several O-methylations, but the biosynthetic gene cluster...
Modification of the polyketide anthraquinone AQ-256 in the entomopathogenic Photorhabdus luminescens involves several O-methylations, but the biosynthetic gene cluster antA-I lacks corresponding tailoring enzymes. We here describe the identification of five putative, highly homologous O-methyltransferases encoded in the genome of P. luminescens. Activity assays in vitro and deletion experiments in vivo revealed that three of them account for anthraquinone tailoring by producing three monomethylated and two dimethylated species of AQ-256. X-ray structures of all five enzymes indicate high structural and mechanistic similarity. As confirmed by structure-based mutagenesis, a conserved histidine at the active site likely functions as a general base for substrate deprotonation and subsequent methyl transfer in all enzymes. Eight complex structures with AQ-256 as well as mono- and dimethylated derivatives confirm the substrate specificity patterns found in vitro and visualize how single amino acid differences in the active-site pockets impact substrate orientation and govern site-specific methylation.
Topics: Methyltransferases; Methylation; Photorhabdus; Catalytic Domain; Anthraquinones
PubMed: 36963398
DOI: 10.1016/j.str.2023.03.001 -
Marine Life Science & Technology Feb 2021Mutation is a primary source of genetic variation that is used to power evolution. Many studies, however, have shown that most mutations are deleterious and, as a...
Mutation is a primary source of genetic variation that is used to power evolution. Many studies, however, have shown that most mutations are deleterious and, as a result, extremely low mutation rates might be beneficial for survival. Using a mutation accumulation experiment, an unbiased method for mutation study, we found an extremely low base-substitution mutation rate of 5.94 × 10 per nucleotide site per cell division (95% Poisson confidence intervals: 4.65 × 10, 7.48 × 10) and indel mutation rate of 8.25 × 10 per site per cell division (95% confidence intervals: 3.96 × 10, 1.52 × 10) in the bacterium ATCC29999. The mutations are strongly A/T-biased with a mutation bias of 10.28 in the A/T direction. It has been hypothesized that the ability for selection to lower mutation rates is inversely proportional to the effective population size (drift-barrier hypothesis) and we found that the effective population size of this bacterium is significantly greater than most other bacteria. This finding further decreases the lower-bounds of bacterial mutation rates and provides evidence that extreme levels of replication fidelity can evolve within organisms that maintain large effective population sizes.
PubMed: 33791681
DOI: 10.1007/s42995-020-00060-0 -
PloS One 2021Xenorhabdus and Photorhabdus are gram negative bacteria that can produce several secondary metabolites, including antimicrobial compounds. They have a symbiotic...
Xenorhabdus and Photorhabdus are gram negative bacteria that can produce several secondary metabolites, including antimicrobial compounds. They have a symbiotic association with entomopathogenic nematodes (EPNs). The aim of this study was to isolate and identify Xenorhabdus and Photorhabdus species and their associated nematode symbionts from Northeastern region of Thailand. We also evaluated the antibacterial activity of these symbiotic bacteria. The recovery rate of EPNs was 7.82% (113/1445). A total of 62 Xenorhabdus and 51 Photorhabdus strains were isolated from the EPNs. Based on recA sequencing and phylogeny, Xenorhabdus isolates were identified as X. stockiae (n = 60), X. indica (n = 1) and X. eapokensis (n = 1). Photorhabdus isolates were identified as P. luminescens subsp. akhurstii (n = 29), P. luminescens subsp. hainanensis (n = 18), P. luminescens subsp. laumondii (n = 2), and P. asymbiotica subsp. australis (n = 2). The EPNs based on 28S rDNA and internal transcribed spacer (ITS) analysis were identified as Steinernema surkhetense (n = 35), S. sangi (n = 1), unidentified Steinernema (n = 1), Heterorhabditis indica (n = 39), H. baujardi (n = 1), and Heterorhabditis sp. SGmg3 (n = 3). Antibacterial activity showed that X. stockiae (bMSK7.5_TH) extract inhibited several antibiotic-resistant bacterial strains. To the best of our knowledge, this is the first report on mutualistic association between P. luminescens subsp. laumondii and Heterorhabditis sp. SGmg3. This study could act as a platform for future studies focusing on the discovery of novel antimicrobial compounds from these bacterial isolates.
Topics: Animals; Anti-Bacterial Agents; Drug Resistance, Bacterial; Gram-Negative Bacteria; Gram-Positive Bacteria; Larva; Microbial Sensitivity Tests; Nematoda; Photorhabdus; Phylogeny; RNA, Ribosomal, 16S; RNA, Ribosomal, 28S; Soil; Soil Microbiology; Symbiosis; Xenorhabdus
PubMed: 34383819
DOI: 10.1371/journal.pone.0255943