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PloS One 2020Xenorhabdus and Photorhabdus, symbiotically associated with entomopathogenic nematodes (EPNs), produce a range of antimicrobial compounds. The objective of this study is...
Xenorhabdus and Photorhabdus, symbiotically associated with entomopathogenic nematodes (EPNs), produce a range of antimicrobial compounds. The objective of this study is to identify Xenorhabdus and Photorhabdus and their EPNs hosts, which were isolated from soil samples from Saraburi province, and study their antibacterial activity against 15 strains of drug-resistant bacteria. Fourteen isolates (6.1%), consisting of six Xenorhabdus isolates and eight Photorhabdus isolates, were obtained from 230 soil samples. Based on the BLASTN search incorporating the phylogenetic analysis of a partial recA gene, all six isolates of Xenorhabdus were found to be identical and closely related to X. stockiae. Five isolates of Photorhabdus were found to be identical and closely related to P. luminescens subsp. akhurstii. Two isolates of Photorhabdus were found to be identical and closely related to P. luminescens subsp. hainanensis. The remaining isolate of Photorhabdus was found to be identical to P. asymbiotica subsp. australis. The bacterial extracts from P. luminescens subsp. akhurstii showed strong inhibition the growth of S. aureus strain PB36 (MSRA) by disk diffusion, minimal inhibitory concentration, and minimal bactericidal concentration assay. The combination between each extract from Xenorhabdus/Photorhabdus and oxacillin or vancomycin against S. aureus strain PB36 (MRSA) exhibited no interaction on checkerboard assay. Moreover, killing curve assay of P. luminescens subsp. akhurstii extracts against S. aureus strain PB36 exhibited a steady reduction of 105 CFU/ml to 103 CFU/ml within 30 min. This study demonstrates that Xenorhabdus and Photorhabdus, showed antibacterial activity. This finding may be useful for further research on antibiotic production.
Topics: Animals; Anti-Bacterial Agents; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Nematoda; Oxacillin; Photorhabdus; Phylogeny; Soil; Vancomycin; Xenorhabdus
PubMed: 32502188
DOI: 10.1371/journal.pone.0234129 -
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 -
PLoS Pathogens May 2023Photorhabdus insect-related toxins A and B (PirA and PirB) were first recognized as insecticidal toxins from Photorhabdus luminescens. However, subsequent studies showed... (Review)
Review
Photorhabdus insect-related toxins A and B (PirA and PirB) were first recognized as insecticidal toxins from Photorhabdus luminescens. However, subsequent studies showed that their homologs from Vibrio parahaemolyticus also play critical roles in the pathogenesis of acute hepatopancreatic necrosis disease (AHPND) in shrimps. Based on the structural features of the PirA/PirB toxins, it was suggested that they might function in the same way as a Bacillus thuringiensis Cry pore-forming toxin. However, unlike Cry toxins, studies on the PirA/PirB toxins are still scarce, and their cytotoxic mechanism remains to be clarified. In this review, based on our studies of V. parahaemolyticus PirAvp/PirBvp, we summarize the current understanding of the gene locations, expression control, activation, and cytotoxic mechanism of this type of toxin. Given the important role these toxins play in aquatic disease and their potential use in pest control applications, we also suggest further topics for research. We hope the information presented here will be helpful for future PirA/PirB studies.
Topics: Animals; Photorhabdus; Penaeidae; Bacterial Proteins; Bacterial Toxins; Insecta; Vibrio parahaemolyticus
PubMed: 37141203
DOI: 10.1371/journal.ppat.1011330 -
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 -
Applied Biochemistry and Biotechnology May 2020Photorhabdus luminescens is an entomopathogenic rod-shaped bacterium infected with insect nematodes of the Heterorhabditidae family. It kills insects through the...
Photorhabdus luminescens is an entomopathogenic rod-shaped bacterium infected with insect nematodes of the Heterorhabditidae family. It kills insects through the secretion of high molecular weight toxin complexes. In this study, Plutella xylostella larvae were orally administered P. luminescens for bioassay. After incubation in Luria-Bertani (LB) medium for a sufficiently long period, the mortality rates of P. xylostella observed after diluting the fermentation broth 50 times and diluting the supernatant 5 times were 18.89% and 91.11%, respectively. Retentates measuring more than 70 kDa showed 88% mortality after ultrafiltration (UF) membrane treatment. Thus, the supernatant of P. luminescens had insecticidal activity, and the main insecticidal toxin complexes had a molecular weight exceeding 70 kDa. The L (3) Taguchi orthogonal experimental optimized medium mode-predicted insecticidal activity levels were 84% and 119% in the 50-fold diluted fermentation broth and 5-fold diluted supernatant, respectively. Moreover, the insecticidal activity was improved to 92.2% in the 100-fold diluted fermentation broth and to 97.8% in the 10-fold diluted supernatant in the experiments. All combinations tested showed clear indications of lethality, including swelling, vesicle formation, cytoplasm vacuolization, and brush border membrane lysis. Thus, these results promote the use of P. luminescens 0805-P2R as a potent biopesticide to effectively control P. xylostella.
Topics: Animals; Bacterial Toxins; Insecticides; Moths; Photorhabdus
PubMed: 32100234
DOI: 10.1007/s12010-020-03289-8 -
International Journal of Systematic and... Oct 2022One motile, Gram-negative, non-spore-forming and rod-shaped symbiotic bacterium, strain UCH-936, was isolated from nematodes. Results of biochemical, physiological,...
One motile, Gram-negative, non-spore-forming and rod-shaped symbiotic bacterium, strain UCH-936, was isolated from nematodes. Results of biochemical, physiological, molecular and genomic analyses suggest that it represents a new species, which we propose to name sp. nov. Digital DNA-DNA hybridization shows that strain UCH-936 is more closely related to DSM 23513, but shares solely 50.5 % similarity, which is below the 70% cut-off value that delimits species boundaries in bacteria. Phylogenetic reconstructions using whole-genome sequences show that strain UCH-936 forms a unique clade, suggesting its novel and distinct taxonomic status again. Similarly, comparative genomic analyses shows that the virulence factor flagella-related gene , the type IV pili-related gene and the vibriobactin-related gene are present in the genome of strain UCH-936 but absent in the genomes of its closest relatives. Biochemically and physiologically, UCH-936 differs also from all closely related species. Therefore, sp. nov. is proposed as a new species with the type strain UCH-936 (CCCT 21.06=CCM 9188=CCOS 1991).
Topics: Animals; Bacterial Typing Techniques; Base Composition; DNA, Bacterial; Fatty Acids; Nematoda; Photorhabdus; Phylogeny; RNA, Ribosomal, 16S; Rhabditoidea; Sequence Analysis, DNA; Virulence Factors
PubMed: 36223180
DOI: 10.1099/ijsem.0.005525 -
Journal of Invertebrate Pathology Oct 2022Photorhabdus insect related proteins A & B (PirA, PirB) from Photorhabdus and Xenorhabdus bacteria exhibit both oral and injectable toxicity against lepidopteran and...
Photorhabdus insect related proteins A & B (PirA, PirB) from Photorhabdus and Xenorhabdus bacteria exhibit both oral and injectable toxicity against lepidopteran and dipteran insect pest. The pirA, pirAt (encoding 6 N-terminal truncated PirA), pirB genes, pirA-pirB (with ERIC sequences), pirA-pirB-mERIC (modified pirA-pirB with mutated ERIC sequences) and polycistronic-pirAB were cloned and expressed in Escherichia coli. However, PirA protein was expressed in insoluble form and therefore the pirA gene was modified to produce PirAt. Moreover, pirA-pirB-mERIC, polycistronic-pirAB and co-transformed pirA/pirB genes were not expressed in the studied prokaryotic expression systems. None of the single purified proteins or mixtures of the individually expressed and purified proteins were toxic to mosquito larvae of Aedes aegypti and Culex quinquefasciatus. However, PirA-PirB protein mixtures purified from pirA-pirB operon plasmid were toxic to A. aegypti and C. quinquefasciatus larvae with LC values of 991 and 614 ng/ml, respectively. The presence of ERIC sequences between the two orfs of the pirA-pirB operon could help to obtain the proteins in biologically active form. Further, results confirm that PirA-PirB proteins of P. akhurstii subsp. akhurstii K-1 are binary insecticidal toxins and ERIC sequences could play an important role in expression of Pir proteins. Reports of biophysical characterization of individually purified PirAt, PirB and expressed PirA-PirB toxin mixture could provide the structural insight into these proteins.
Topics: Animals; Bacterial Proteins; Bacterial Toxins; Escherichia coli; Insect Proteins; Larva; Photorhabdus; Xenorhabdus
PubMed: 36167186
DOI: 10.1016/j.jip.2022.107829 -
Biology Oct 2021and are considered a global threat to agricultural crops and food security; hence, their control is a critical issue. and nematodes, along with their symbiotic...
and are considered a global threat to agricultural crops and food security; hence, their control is a critical issue. and nematodes, along with their symbiotic bacteria, can achieve the optimal biocontrol agent criterion. Therefore, this study aimed to evaluate the efficacy of , and their symbiotic bacteria ( and ) against and larvae. The virulence of entomopathogenic nematodes (EPNs) was determined at different infective juvenile concentrations and exposure times, while the symbiotic bacteria were applied at the concentration of 3 × 10 colony-forming units (CFU)/mL at different exposure times. Gas chromatography-mass spectrophotometry (GC-MS) analysis and the cytotoxic effect of sp. and sp. were determined. The results indicated that . , . , and their symbiotic bacteria significantly ( ≤ 0.001) induced mortality in both insect species. However, . and its symbiont, sp., were more virulent. Moreover, the data clarified that both symbiotic bacteria outperformed EPNs against but the opposite was true for GC-MS analysis revealed the main active compounds that have insecticidal activity. However, the results revealed that there was no significant cytotoxic effect. In conclusion, . , . , and their symbiotic bacteria can be an optimal option for bio-controlling both insect species. Furthermore, both symbiotic bacteria can be utilized independently on EPNs for the management of both pests, and, hence, they can be safely incorporated into biocontrol programs and tested against other insect pests.
PubMed: 34681098
DOI: 10.3390/biology10100999 -
Frontiers in Microbiology 2019A major issue currently facing medicine is antibiotic resistance. No new class of antibiotics for the treatment of Gram-negative infections has been introduced in more... (Review)
Review
A major issue currently facing medicine is antibiotic resistance. No new class of antibiotics for the treatment of Gram-negative infections has been introduced in more than 40 years. We screened a collection of and strains in the quest to discover new structures that are active against the most problematic multidrug-resistant bacteria. These species are symbiotic bacteria of entomopathogenic nematodes and their life cycle, the richness of the bacteria's genome in non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) genes, and their propensity to produce secondary metabolites with a large diversity of chemical structures make them a good starting point to begin an ambitious drug discovery program. Odilorhabdins (ODLs), a novel antibacterial class, were identified from this campaign. These compounds inhibit bacterial translation by binding to the small ribosomal subunit at a site not exploited by current antibiotics. Following the development of the total synthesis of this family of peptides, a medicinal chemistry program was started to optimize their pharmacological properties. NOSO-502, the first ODL preclinical candidate was selected. This compound is currently under preclinical development for the treatment of multidrug-resistant Gram-negative infections in hospitalized patients.
PubMed: 31921069
DOI: 10.3389/fmicb.2019.02893 -
Environmental Microbiology Reports Dec 2022Photorhabdus, the symbiotic bacteria of Heterorhabditis nematodes, has been reported to possess many non-ribosomal peptide synthetase (NRPS) biosynthesis gene clusters...
Photorhabdus, the symbiotic bacteria of Heterorhabditis nematodes, has been reported to possess many non-ribosomal peptide synthetase (NRPS) biosynthesis gene clusters (BGCs). To provide an in-depth assessment of the non-ribosomal peptide biosynthetic potential of Photorhabdus, we compared the distribution of BGCs in 81 Photorhabdus strains, confirming the predominant presence (44.80%) of NRPS BGCs in Photorhabdus. All 990 NRPS BGCs were clustered into 275 gene cluster families (GCFs) and only 13 GCFs could be annotated with known BGCs, suggesting their great diversity and novelty. These NRPS BGCs encoded 351 novel peptides containing more than four amino acids, and 173 of them showed high sequence similarity to known BGCs encoding bioactive peptides, implying the promising potential of Photorhabdus to produce valuable peptides. Sequence similarity networking of adenylation (A-) domains suggested that the substrate specificity of A-domains was not directly correlated with the sequence similarity. The molecular similarity network of predicted metabolite scaffolds of NRPS BGCs and reported peptides from Photorhabdus and a relevant database demonstrated that the non-ribosomal peptide biosynthetic potential of Photorhabdus was largely untapped and revealed the core peptides deserving intensive studies. Our present study provides valuable information for the targeted discovery of novel non-ribosomal peptides from Photorhabdus.
Topics: Animals; Photorhabdus; Nematoda; Multigene Family; Symbiosis; Peptides
PubMed: 35998886
DOI: 10.1111/1758-2229.13118