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Frontiers in Microbiology 2022Phylum Nematoda is of great economic importance. It has been a focused area for various research activities in distinct domains across the globe. Among nematodes, there... (Review)
Review
Phylum Nematoda is of great economic importance. It has been a focused area for various research activities in distinct domains across the globe. Among nematodes, there is a group called entomopathogenic nematodes, which has two families that live in symbiotic association with bacteria of genus and , respectively. With the passing years, researchers have isolated a wide array of bioactive compounds from these symbiotically associated nematodes. In this article, we are encapsulating bioactive compounds isolated from members of the family Heterorhabditidae inhabiting in its gut. Isolated bioactive compounds have shown a wide range of biological activity against deadly pathogens to both plants as well as animals. Some compounds exhibit lethal effects against fungi, bacteria, protozoan, insects, cancerous cell lines, neuroinflammation, etc., with great potency. The main aim of this article is to collect and analyze the importance of nematode and its associated bacteria, isolated secondary metabolites, and their biomedical potential, which can serve as potential leads for further drug discovery.
PubMed: 35422783
DOI: 10.3389/fmicb.2022.790339 -
Engineering in Life Sciences Mar 2022A possible solution for the standoff detection of buried landmines is based on the use of microbial bioreporters, genetically engineered to emit a remotely detectable...
A possible solution for the standoff detection of buried landmines is based on the use of microbial bioreporters, genetically engineered to emit a remotely detectable optical signal in response to trace amounts of explosives' signature chemicals, mostly 2,4-dinitrotoluene (DNT). Previously developed DNT sensor strains were based on the fusion of a DNT-inducible gene promoter to a reporting element, either a fluorescent protein gene or a bacterial bioluminescence gene cassette. In the present study, a different approach was used: the DNT-inducible promoter activates, in , the quorum-sensing and genes of . N-Acyl homoserine lactone (AHL), synthesized by LuxI, combines with LuxR and activates the bioluminescence reporter genes. The resulting bioreporter displayed a dose-dependent luminescent signal in the presence of DNT. Performance of the sensor strain was further enhanced by manipulation of the sensing element (combining the DNT-inducible and gene promoters), by replacing the luminescence gene cassette of with , and by introducing two mutations, and , into the host strain. DNT detection sensitivity of the final bioreporter was over 340-fold higher than the original construct.
PubMed: 35382532
DOI: 10.1002/elsc.202100134 -
Microorganisms Feb 2022Bacteria of the genera and are symbionts of entomopathogenic nematodes. Despite their close phylogenetic relationship, they show differences in their pathogenicity and...
Bacteria of the genera and are symbionts of entomopathogenic nematodes. Despite their close phylogenetic relationship, they show differences in their pathogenicity and virulence mechanisms in target insects. These differences were explored by the analysis of the pangenome, as it provides a framework for characterizing and defining the gene repertoire. We performed the first pangenome analysis of 91 strains of and ; the analysis showed that the genus has a higher number of genes associated with pathogenicity. However, biological tests showed that whole cells of SC 0516 were more virulent than those of HIM3 when both were injected into larvae. In addition, we cloned and expressed the GroEL proteins of both bacteria, as this protein has been previously indicated to show insecticidal activity in the genus . Among these proteins, Cpn60-Xn was found to be the most toxic at all concentrations tested, with an LC50 value of 102.34 ng/larva. Sequence analysis suggested that the Cpn60-Xn toxin was homologous to Cpn60-Pl; however, Cpn60-Xn contained thirty-five differentially substituted amino acid residues that could be responsible for its insecticidal activity.
PubMed: 35336062
DOI: 10.3390/microorganisms10030486 -
Acta Tropica Jun 2022Heterorhabditis bacteriophora is an entomopathogenic nematode (EPN) that is mutually associated with Photorhabdus luminescens, utilized globally for biological control...
Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae), isolate HP88, induces reproductive and physiological alterations in Biomphalaria glabrata (Gastropoda: Planorbidae): an alternative for biological control of schistosomiasis.
Heterorhabditis bacteriophora is an entomopathogenic nematode (EPN) that is mutually associated with Photorhabdus luminescens, utilized globally for biological control of numerous organisms. Freshwater snails of the species Biomphalaria glabrata have been incriminated as the main intermediate hosts of Schistosoma mansoni in Brazil, but virtually nothing is known about the susceptibility of these gastropod to EPNs. Information in this respect is relevant for control of these intermediate hosts, and thus of the helminthiases they transmit. This paper for the first time reports the susceptibility of B. glabrata to infective juveniles of H. bacteriophora (isolate HP88) under laboratory conditions. For that purpose, six groups were formed: three Control groups (not exposed) and three Treated groups, in which the snails were exposed to 300 juveniles infecting the nematode over three weeks. The entire experiment was conducted in triplicate, using a total of 270 snails. Significant physiological alterations in B. glabrata were observed in response to the infection by H. bacteriophora HP88, characterized by decreased levels of hemolymphatic glucose as well as reduced contents of glycogen stored in the host's digestive gland. In parallel, the hemolymphatic activity of lactate dehydrogenase increased in the infected snails, indicating that the infection induces breakdown of carbohydrate homeostasis in B. glabrata. Additionally, all the reproductive parameters analyzed were reduced as a consequence of the infection. The results indicate the occurrence of the phenomenon of parasitic castration in the B. glabrata/H. bacteriophora HP88 interface, probably due to the depletion of galactogen in the parasitized organism. Although the infection did not cause lethality in the population of infected snails, H. bacteriophora HP88 compromised the reproductive performance of B. glabrata, suggesting its applicability in programs for biological control of this planorbid.
Topics: Animals; Biomphalaria; Rhabditida; Schistosoma mansoni; Schistosomiasis; Snails
PubMed: 35283103
DOI: 10.1016/j.actatropica.2022.106396 -
Biology Feb 2022(Lepidoptera: Lycaenidae) and (Lepidoptera: Pyralidae) are the key pests of pomegranates in Saudi Arabia that are managed mainly using broad-spectrum pesticides....
Isolation, Identification, and Biocontrol Potential of Entomopathogenic Nematodes and Associated Bacteria against (Lepidoptera: Lycaenidae) and (Lepidoptera: Pyralidae).
(Lepidoptera: Lycaenidae) and (Lepidoptera: Pyralidae) are the key pests of pomegranates in Saudi Arabia that are managed mainly using broad-spectrum pesticides. Interactions between the entomopathogenic nematodes (EPNs) Steinernematids, and Heterorhabditids, and their entomopathogenic bacterial symbionts (EPBs) have long been considered monoxenic 2-partner associations responsible for killing insects and, therefore, are widely used in insect pest biocontrol. However, there are limited reports identifying such organisms in Taif, Saudi Arabia. The current study aimed to identify the EPNs and their associated bacteria isolated from Taif, Saudi Arabia, and evaluate their biocontrol potential on third instar larvae of and under laboratory conditions. A total of 35 EPN isolates belonging to (20) and (15) were recovered from 320 soil samples. Twenty-six isolates of symbiotic or associated bacteria were isolated from EPNs and molecularly identified as (6 isolates), (4 isolates), (7), or (9). A pathogenicity assay revealed that spp. were more virulent than spp. against the two pomegranate insects, with LC values of 18.5 and 13.6 infective juveniles (IJs)/larva of for spp. and 52 and 32.4 IJs/larva of for spp. at 48 and 72 h post-treatment, respectively. Moreover, LC values of 9 and 6.6 IJs/larva ( spp.) and 34.4 and 26.6 IJs/larva ( spp.) were recorded for larvae at 48 and 72 h post-treatment. In addition, the EPB CQ1, isolated from spp., surpassed SJ10, associated with spp., in their ability to kill or larvae within 6 h post-application, resulting in 100% mortality in both insects after 24 and 48 h of exposure. We conclude that either application of EPNs' IJs or their associated EPBs could serve as potential biocontrol agents for and .
PubMed: 35205161
DOI: 10.3390/biology11020295 -
Frontiers in Veterinary Science 2021Acute hepatopancreatic necrosis disease (AHPND), formerly called early mortality syndrome (EMS), causes high mortality in cultured penaeid shrimp, particularly and ....
Acute hepatopancreatic necrosis disease (AHPND), formerly called early mortality syndrome (EMS), causes high mortality in cultured penaeid shrimp, particularly and . AHPND is mainly caused by species carrying the pVA1 plasmid encoding the virulence genes Photorhabdus insect-related () and . We developed a new molecular assay that combines recombinase polymerase amplification (RPA) and CRISPR/Cas12a technology (RPA-CRISPR/Cas12a) to detect and , with a fluorescent signal result. The fluorescence RPA-CRISPR/Cas12a assay had a detection limit of 20 copies/μL for and . To improve usability and visualize RPA-CRISPR/Cas12a assay results, a lateral flow strip readout was added. With the lateral flow strip, the RPA-CRISPR/Cas12a assay had a lower limit of detection of 200 copies/μL (0.3 fmol/L). The lateral flow assay can be completed in 2 h and showed no cross-reactivity with pathogens causing other shrimp diseases. In a field test of 60 shrimp samples, the RPA-CRISPR/Cas12a lateral flow assay showed 92.5% positive predictive agreement and 100% negative predictive agreement. As the new RPA-CRISPR/Cas12a assay is rapid, specific, and does not require complicated experimental equipment, it may have important field applications for detecting AHPND in farmed shrimp.
PubMed: 35146019
DOI: 10.3389/fvets.2021.819681 -
Microbiology Spectrum Feb 2022Entomopathogenic bacteria (Enterobacteriaceae: Gamma-proteobacteria), the natural symbionts of nematodes, are a rich source for the discovery of biologically active...
Selective Toxicity of Secondary Metabolites from the Entomopathogenic Bacterium Photorhabdus luminescens against Selected Plant Parasitic Nematodes of the Tylenchina Suborder.
Entomopathogenic bacteria (Enterobacteriaceae: Gamma-proteobacteria), the natural symbionts of nematodes, are a rich source for the discovery of biologically active secondary metabolites (SMs). This study describes the isolation of three nematicidal SMs from culture supernatants of the Arizona-native Photorhabdus luminescens strain Caborca by bioactivity-guided fractionation. Nuclear magnetic resonance spectroscopy and comparison to authentic synthetic standards identified these bioactive metabolites as -cinnamic acid (-CA), (4)-5-phenylpent-4-enoic acid (PPA), and indole. PPA and CA displayed potent, concentration-dependent nematicidal activities against the root-knot nematode (Meloidogyne incognita) and the citrus nematode (), two economically and globally important plant parasitic nematodes (PPNs) that are ubiquitous in the United States. Southwest. Indole showed potent, concentration-dependent nematistatic activity by inducing the temporary rigid paralysis of the same targeted nematodes. While paralysis was persistent in the presence of indole, the nematodes recovered upon removal of the compound. All three SMs were found to be selective against the tested PPNs, exerting little effects on non-target species such as the bacteria-feeding nematode Caenorhabditis elegans or the entomopathogenic nematodes Steinernema carpocapsae, Heterorhabditis bacteriophora, and . Moreover, none of these SMs showed cytotoxicity against normal or neoplastic human cells. The combination of CA + PPA + indole had a synergistic nematicidal effect on both targeted PPNs. Two-component mixtures prepared from these SMs revealed complex, compound-, and nematode species-dependent interactions. These results justify further investigations into the chemical ecology of SMs, and recommend CA, PPA and indole, alone or in combinations, as lead compounds for the development of selective and environmentally benign nematicides against the tested PPNs. Two phenylpropanoid and one alkaloid secondary metabolites were isolated and identified from culture filtrates of strain Caborca. The three identified metabolites showed selective nematicidal and/or nematistatic activities against two important plant parasitic nematodes, the root-knot nematode (Meloidogyne incognita) and the citrus nematode (). The mixture of all three metabolites had a synergistic nematicidal effect on both targeted nematodes, while other combinations showed compound- and nematode-dependent interactions.
Topics: Animals; Anthelmintics; Cinnamates; Indoles; Molecular Structure; Photorhabdus; Plant Diseases; Secondary Metabolism; Tylenchoidea
PubMed: 35138171
DOI: 10.1128/spectrum.02577-21 -
Brazilian Journal of Biology = Revista... 2022Sugarcane crops Saccharum spp. (Poales: Poaceae) produces different derivatives to the world: sugar, ethanol and bioenergy. Despite the application of pesticides, insect...
Virulence of entomopathogenic nematodes and their symbiotic bacteria, under laboratory conditions, aiming controlling Saccharicoccus sacchari (Cockerell, 1895) (Hemiptera: Pseudococcidae) on sugarcane.
Sugarcane crops Saccharum spp. (Poales: Poaceae) produces different derivatives to the world: sugar, ethanol and bioenergy. Despite the application of pesticides, insect pests still cause economic losses, among these the pink sugarcane mealybug Saccharicoccus sacchari (Cockerell, 1895) (Hemiptera: Pseudococcidae) causing direct and indirect damage to the plant. This study assess the virulence of three entomopathogenic nematodes (EPNs) species and their symbiont bacteria against the pink sugarcane mealybug, under laboratory conditions. Fourteen treatments represented by control (distilled water), Heterorhabditis bacteriophora Poinar, 1976 (HB EN01) (Rhabditida: Heterorhabditidae), Steinernema rarum (Doucet, 1986) (PAM25) and Steinernema carpocapsae Weiser, 1955 (All) (Rhabditida: Steinermatidae) at concentrations of 25, 50, 75 and 100 infective juveniles (IJs)/insect, and the standard chemical product, thiamethoxam, were assayed. In a second experiment, the bacteria Photorhabdus luminescens (Thomas and Poinar, 1979), Xenorhabdus szentirmaii Lengyel, 2005 and Xenorhabdus nematophila (Poinar and Thomas, 1965) (Enterobacterales: Morganellaceae) at 3.0 x 109 cells/ml were assessed for each treatment. Ten replications were stablished, each one counting ten females/mealybugs inside a 10 cm Petri dish, amounting 100 individuals/treatment. All treatments were kept under stable conditions (25±1 ºC, H 70±10%, in the dark). All nematodes species infected S. sacchari. Steinerma rarum (PAM25) provided the highest mortality against the pink sugarcane mealybug (79.25%), followed by H. bacteriophora (HB EN01) (58.25%) and S. carpocapsae (All) (42.50%) (P<0.001). The mortality rate caused by X. szentirmaii, P. luminescens and X. nematophila were 40, 45 and 20%, respectively. Steinerma rarum (PAM25) has conditions to be a potential agent to be incorporate into the integrated pest management in sugarcane.
Topics: Animals; Bacteria; Female; Hemiptera; Humans; Laboratories; Pest Control, Biological; Rhabditida; Saccharum; Virulence
PubMed: 35137847
DOI: 10.1590/1519-6984.253780 -
MBio Feb 2022Antibiotic resistance is an increasing threat to human health. A direct link has been established between antimicrobial self-resistance determinants of antibiotic...
Antibiotic resistance is an increasing threat to human health. A direct link has been established between antimicrobial self-resistance determinants of antibiotic producers, environmental bacteria, and clinical pathogens. Natural odilorhabdins (ODLs) constitute a new family of 10-mer linear cationic peptide antibiotics inhibiting bacterial translation by binding to the 30S subunit of the ribosome. These bioactive secondary metabolites are produced by entomopathogenic bacterial symbiont (), vectored by the soil-dwelling nematodes. ODL-producing Xenorhabdus nematophila symbionts have mechanisms of self-protection. In this study, we cloned the 44.5-kb biosynthetic gene cluster (-BGC) of the symbiont by recombineering and showed that the -acetyltransferase-encoding gene, , is responsible for ODL resistance. acetylation and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses showed that OatA targeted the side chain amino group of ODL rare amino acids, leading to a loss of translation inhibition and antibacterial properties. Functional, genomic, and phylogenetic analyses of revealed an exclusive -link to the odilorhabdin BGC, found only in and a specific phylogenetic clade of . This work highlights the coevolution of antibiotic production and self-resistance as ancient features of this unique tripartite complex of host-vector-symbiont interactions without -BGC dissemination by lateral gene transfer. Odilorhabdins (ODLs) constitute a novel antibiotic family with promising properties for treating problematic multidrug-resistant Gram-negative bacterial infections. ODLs are 10-mer linear cationic peptides inhibiting bacterial translation by binding to the small subunit of the ribosome. These natural peptides are produced by Xenorhabdus nematophila, a bacterial symbiont of entomopathogenic nematodes well known to produce large amounts of specialized secondary metabolites. Like other antimicrobial producers, ODL-producing Xenorhabdus nematophila has mechanisms of self-protection. In this study, we cloned the ODL-biosynthetic gene cluster of the symbiont by recombineering and showed that the -acetyltransferase-encoding gene, , is responsible for ODL resistance. acetylation and LC-MS/MS analyses showed that OatA targeted the side chain amino group of ODL rare amino acids, leading to a loss of translation inhibition and antibacterial properties. Functional, genomic, and phylogenetic analyses of revealed the coevolution of antibiotic production and self-resistance as ancient feature of this particular niche in soil invertebrates without resistance dissemination.
Topics: Animals; Humans; Phylogeny; Acetyltransferases; Chromatography, Liquid; Tandem Mass Spectrometry; Bacteria; Nematoda; Xenorhabdus; Anti-Infective Agents; Anti-Bacterial Agents
PubMed: 35012352
DOI: 10.1128/mbio.02826-21 -
Frontiers in Immunology 2021The multifaceted functions ranging from cellular and developmental mechanisms to inflammation and immunity have rendered TGF-ß signaling pathways as critical regulators...
The multifaceted functions ranging from cellular and developmental mechanisms to inflammation and immunity have rendered TGF-ß signaling pathways as critical regulators of conserved biological processes. Recent studies have indicated that this evolutionary conserved signaling pathway among metazoans contributes to the anti-nematode immune response. However, functional characterization of the interaction between TGF-ß signaling activity and the mechanisms activated by the immune response against parasitic nematode infection remains unexplored. Also, it is essential to evaluate the precise effect of entomopathogenic nematode parasites on the host immune system by separating them from their mutualistic bacteria. Here, we investigated the participation of the TGF-ß signaling branches, activin and bone morphogenetic protein (BMP), to host immune function against axenic or symbiotic nematodes (parasites lacking or containing their mutualistic bacteria, respectively). Using larvae carrying mutations in the genes coding for the TGF-ß extracellular ligands Daw and Dpp, we analyzed the changes in survival ability, cellular immune response, and phenoloxidase (PO) activity during nematode infection. We show that infection with axenic decreases the mortality rate of mutants, but not mutants. Following axenic or symbiotic . infection, both and mutants contain only plasmatocytes. We further detect higher levels of gene expression in mutants upon infection with axenic nematodes and and gene expression in mutants upon infection with symbiotic nematodes compared to controls. Finally, following symbiotic infection, mutants have higher PO activity relative to controls. Together, our findings reveal that while Dpp/BMP signaling activity modulates the DUOX/ROS response to axenic infection, Daw/activin signaling activity modulates the antimicrobial peptide and melanization responses to axenic infection. Results from this study expand our current understanding of the molecular and mechanistic interplay between nematode parasites and the host immune system, and the involvement of TGF-ß signaling branches in this process. Such findings will provide valuable insight on the evolution of the immune role of TGF-ß signaling, which could lead to the development of novel strategies for the effective management of human parasitic nematodes.
Topics: Activins; Animals; Bone Morphogenetic Proteins; Cecropins; Drosophila Proteins; Drosophila melanogaster; Dual Oxidases; Host-Parasite Interactions; Insect Proteins; Mutation; Reactive Oxygen Species; Rhabditida; Rhabditida Infections; Signal Transduction; Transforming Growth Factor beta
PubMed: 35003118
DOI: 10.3389/fimmu.2021.795331