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The Journal of General and Applied... May 2024There are a number of reporter systems that are useful for gene expression analysis in bacteria. However, at least in Salmonella, a versatile and simple luciferase...
There are a number of reporter systems that are useful for gene expression analysis in bacteria. However, at least in Salmonella, a versatile and simple luciferase reporter system that can be integrated precisely behind a promoter or gene of interest on a chromosome is not currently available. The luciferase operon luxCDABE from Photorhabdus luminescens has several advantages, including brightness, wide linear range, absence in most bacteria, stability at high temperature, and no substrate addition required for the assay. Here, a conjugation-mediated site-specific single-copy luciferase fusion system is developed. A reporter plasmid containing the conditional replication origin R6Kgγ, FRT-luxCDABE, and Km marker was designed to be incorporated into the FRT site behind the promoter or gene of interest on the chromosome in cells expressing FLP. However, when this reporter plasmid was electroporated directly into such a S. enterica strain, no colonies appeared, likely due to the low transformation efficiency of this relatively large plasmid DNA. Meanwhile, the same reporter plasmid was successfully introduced and launched as an insert of an FRT-containing conjugative transfer plasmid from a mating E. coli strain to the same recipient S. enterica strain, as well as Citrobacter koseri. RcsB-dependent inducible luminescence from the constructed wzc-luxCDABE strains was confirmed. This system is feasible for detecting very low levels of transcription, even in Gram-negative bacterial species that are relatively difficult to genetically manipulate.
Topics: Plasmids; Genes, Reporter; Luciferases; Photorhabdus; Conjugation, Genetic; Escherichia coli; Promoter Regions, Genetic; Operon; Salmonella enterica
PubMed: 37940551
DOI: 10.2323/jgam.2023.10.001 -
MicroPublication Biology 2023The fruit fly is an excellent model for dissecting the molecular and functional bases of bacterial pathogenicity and host antibacterial immune response. The...
The fruit fly is an excellent model for dissecting the molecular and functional bases of bacterial pathogenicity and host antibacterial immune response. The Gram-negative bacterium is an insect-specific pathogen that forms a mutualistic relationship with the entomopathogenic nematode . Here we find that oral infection of larvae with moderately reduces their survival ability while the bacteria replicate efficiently in the infected insects. This information will contribute towards understanding host gut immunity against potent bacterial pathogens.
PubMed: 37711508
DOI: 10.17912/micropub.biology.000938 -
Frontiers in Microbiology 2023An entomopathogenic bacterium, subsp. , is mutualistic to its host nematode, . The infective juvenile nematodes enter target insects through natural openings and...
Manipulation of GameXPeptide synthetase gene expression by a promoter exchange alters the virulence of an entomopathogenic bacterium, , by modulating insect immune responses.
An entomopathogenic bacterium, subsp. , is mutualistic to its host nematode, . The infective juvenile nematodes enter target insects through natural openings and release the symbiotic bacteria into the insect hemocoel. The released bacteria suppress the insect immune responses and cause septicemia through their secondary metabolites. GameXPeptide (GXP) is one of the common secondary metabolites of most species and is produced by the catalytic activity of a specific non-ribosomal peptide synthetase called GxpS encoded by the gene. This study confirmed to be encoded in the genome and analyzed its expression during bacterial growth. LC-MS/MS analysis of the bacterial culture broth contained at least four different GXPs (GXP-A to GXP-D), in which GXP-A was the most abundant. To investigate GXP synthesis following expression, the promoter of was replaced with an inducible arabinose promoter by homologous recombination. The transcript levels in the mutant were altered by the addition of l-arabinose. Without the inducer, the transcript level was significantly lower compared to the wild type and produced significantly lower amounts of the four GXPs. The addition of the inducer to the mutant significantly increased expression and produced significantly higher levels of the four GXPs compared to the wild type. The metabolite extracts obtained from wild-type and mutant bacteria showed differential immunosuppressive activities according to their GXP contents against the cellular and humoral immune responses of a lepidopteran insect, . Interestingly, the -mutant bacteria showed less insecticidal activity compared to the wild type, whereas the addition of GXP to the mutant significantly restored insecticidal activity. These results suggest that the gene encoded in is responsible for the production of at least four different GXPs, which play crucial roles in bacterial virulence.
PubMed: 38173677
DOI: 10.3389/fmicb.2023.1271764 -
Developmental and Comparative Immunology Feb 2024Two bacterial genera, Xenorhabdus and Photorhabdus, are mutually symbiotic to the entomopathogenic nematodes, Steinernema and Heterorhabditis, respectively. The...
Two bacterial genera, Xenorhabdus and Photorhabdus, are mutually symbiotic to the entomopathogenic nematodes, Steinernema and Heterorhabditis, respectively. The infective juveniles deliver the symbiotic bacteria to the hemocoel of target insects, in which the bacteria proliferate and help the development of the host nematode. The successful parasitism of the nematode-bacterial complex depends on host immunosuppression by the bacteria via their secondary metabolites. Leucine-responsive regulatory protein (Lrp) is a global bacterial transcriptional factor that plays a crucial role in parasitism. However, its regulatory targets to suppress insect immunity are not clearly understood. This study investigated the bacterial genes regulated by Lrp and the subsequent production of secondary metabolites in Xenorhabdus hominickii. Lrp expression occurred at the early infection stage of the bacteria in a target insect, Spodoptera exigua. A preliminary in silico screening indicated that 3.7% genes among 4075 predicted genes encoded in X. hominickii had the Lrp-response element on their promoters, including two non-ribosomal peptide synthetases (NRPSs). Eight NRPS (NRPS1-NRPS8) genes were predicted in the bacterial genome, in which six NRPS (NRPS3-NRPS8) expressions were positively correlated with Lrp expression in the infected larvae of S. exigua. Exchange of the Lrp promoter with an inducible promoter altered the production of the secondary metabolites and the NRPS expression levels. The immunosuppressive activities of X. hominickii were dependent on the Lrp expression level. The metabolites produced by Lrp expression included the eicosanoid-biosynthesis inhibitors and hemolytic factors. A cyclic dipeptide (=cPF) was produced by the bacteria at high Lrp expression and inhibited the phospholipase A activity of S. exigua in a competitive inhibitory manner. These results suggest that Lrp is a global transcriptional factor of X. hominickii and plays a crucial role in insect immunosuppression by modulating NRPS expression.
Topics: Animals; Leucine-Responsive Regulatory Protein; Xenorhabdus; Nematoda; Peptide Synthases; Transcription Factors; Spodoptera; Symbiosis
PubMed: 38000489
DOI: 10.1016/j.dci.2023.105101 -
Frontiers in Microbiology 2023[This corrects the article DOI: 10.3389/fmicb.2020.00366.].
[This corrects the article DOI: 10.3389/fmicb.2020.00366.].
PubMed: 37886070
DOI: 10.3389/fmicb.2023.1302833 -
Insect Biochemistry and Molecular... Jan 2024Txp40 is a ubiquitous, conserved, and novel toxin from Xenorhabdus and Photorhabdus bacteria, toxic to a wide range of insect pests. However, the three-dimensional...
The crystal structure of insecticidal protein Txp40 from Xenorhabdus nematophila reveals a two-domain unique binary toxin with homology to the toxin-antitoxin (TA) system.
Txp40 is a ubiquitous, conserved, and novel toxin from Xenorhabdus and Photorhabdus bacteria, toxic to a wide range of insect pests. However, the three-dimensional structure and toxicity mechanism for Txp40 or any of its sequence homologs are not yet known. Here, we are reporting the crystal structure of the insecticidal protein Txp40 from Xenorhabdus nematophila at 2.08 Å resolution. The Txp40 was structurally distinct from currently known insecticidal proteins. Txp40 consists of two structurally different domains, an N-terminal domain (NTD) and a C-terminal domain (CTD), primarily joined by a 33-residue long linker peptide. Txp40 displayed proteolytic propensity. Txp40 gets proteolyzed, removing the linker peptide, which is essential for proper crystal packing. NTD adopts a novel fold composed of nine amphipathic helices and has no shared sequence or structural homology to any known proteins. CTD has structural homology with RNases of type II toxin-antitoxin (TA) complex belonging to the RelE/ParE toxin domain superfamily. NTD and CTD were individually toxic to Galleria mellonella larvae. However, maximal toxicity was observed when both domains were present. Our results suggested that the Txp40 acts as a two-domain binary toxin, which is unique and different from any known binary toxins and insecticidal proteins. Txp40 is also unique because it belongs to the prokaryotic RelE/ParE toxin family with a toxic effect on eukaryotic organisms, in contrast to other members of the same family. Broad insect specificity and unique binary toxin complex formation make Txp40 a viable candidate to overcome the development of resistance in insect pests.
Topics: Animals; Insecticides; Xenorhabdus; Bacterial Proteins; Insecta; Antitoxins; Peptides
PubMed: 38040266
DOI: 10.1016/j.ibmb.2023.104045 -
Animals : An Open Access Journal From... May 2024Acute hepatopancreatic necrosis disease (AHPND) poses a significant threat to shrimp aquaculture worldwide, necessitating the accurate and rapid detection of the...
Acute hepatopancreatic necrosis disease (AHPND) poses a significant threat to shrimp aquaculture worldwide, necessitating the accurate and rapid detection of the pathogens. However, the increasing number of species that cause the disease makes diagnosis and control more difficult. This study focuses on developing a monoclonal antibody against the insect-related (Pir) toxin B (PirB), a pivotal virulence factor in AHPND-causing , and establishing a colloidal gold immunochromatographic assay for the enhanced early diagnosis and monitoring of AHPND. Monoclonal antibodies targeting PirB were developed and utilized in the preparation of colloidal-gold-labeled antibodies for the immunochromatographic assay. The specificity and sensitivity of the assay were evaluated through various tests, including antibody subclass detection, affinity detection, and optimal labeling efficiency assessment. The developed PirB immunochromatographic test strips exhibited a good specificity, as demonstrated by the positive detection of AHPND-causing and negative results for non-AHPND-causing . The study highlights the potential of the developed monoclonal antibody and immunochromatographic assay for the effective detection of AHPND-causing . Further optimization is needed to enhance the sensitivity of the test strips for improved practical applications in disease prevention and control in shrimp aquaculture.
PubMed: 38891648
DOI: 10.3390/ani14111600 -
Journal of Fungi (Basel, Switzerland) Feb 2024Fungal diseases such as Fusarium head blight (FHB) are significant biotic stressors, negatively affecting wheat production and quality. This study explored the...
Fungal diseases such as Fusarium head blight (FHB) are significant biotic stressors, negatively affecting wheat production and quality. This study explored the antifungal activity of the metabolites produced by the bacterial symbionts of entomopathogenic nematodes (EPNs) against FHB-causing sp. . To achieve this, the symbiotic bacteria of nine EPN isolates from the EPN collection at the Agricultural Research Council-Small Grains (ARC-SG) were isolated from the cadavers of (Lepidoptera: ) larvae after infection with EPNs. Broth cultures (crude) and their supernatants (filtered and autoclaved) of each bacterial isolate were used as bacterial metabolite treatments to test their inhibitory effect on the mycelial growth and spore germination of . Mycelial growth inhibition rates varied among both bacterial isolates and treatments. Crude metabolite treatments proved to be more effective than filtered and autoclaved metabolite treatments, with an overall inhibition rate of 75.25% compared to 23.93% and 13.32%, respectively. From the crude metabolite treatments, the SGI 197 bacterial isolate from SGI 197 had the highest mean inhibition rate of 96.25%, followed by SGI 170 bacteria isolated from SGI 170 with a 95.79% mean inhibition rate. The filtered metabolite treatments of all bacterial isolates were tested for their inhibitory activity against spore germination. Mean spore germination inhibition rates from spp. bacterial isolates were higher (83.91 to 96.29%) than those from spp. (6.05 to 14.74%). The results obtained from this study suggest that EPN symbiotic bacterial metabolites have potential use as biological control agents of FHB. Although field efficacy against FHB was not studied, the significant inhibition of mycelial growth and spore germination suggest that the application of these metabolites at the flowering stage may provide protection to plants against infection with or spread of . These metabolites have the potential to be employed as part of integrated pest management (IPM) to inhibit/delay conidia germination until the anthesis (flowering stage) of wheat seedlings has passed.
PubMed: 38392820
DOI: 10.3390/jof10020148 -
Antibiotics (Basel, Switzerland) Sep 2023Anti-microbial peptides provide a powerful toolkit for combating multidrug resistance. Combating eukaryotic pathogens is complicated because the intracellular drug...
Anti-microbial peptides provide a powerful toolkit for combating multidrug resistance. Combating eukaryotic pathogens is complicated because the intracellular drug targets in the eukaryotic pathogen are frequently homologs of cellular structures of vital importance in the host organism. The entomopathogenic bacteria (EPB), symbionts of entomopathogenic-nematode species, release a series of non-ribosomal templated anti-microbial peptides. Some may be potential drug candidates. The ability of an entomopathogenic-nematode/entomopathogenic bacterium symbiotic complex to survive in a given polyxenic milieu is a coevolutionary product. This explains that those gene complexes that are responsible for the biosynthesis of different non-ribosomal templated anti-microbial protective peptides (including those that are potently capable of inactivating the protist mammalian pathogen and the gallinaceous bird pathogen ) are co-regulated. Our approach is based on comparative anti-microbial bioassays of the culture media of the wild-type and regulatory mutant strains. We concluded that and are excellent sources of non-ribosomal templated anti-microbial peptides that are efficient antagonists of the mentioned pathogens. Data on selective cytotoxicity of different cell-free culture media encourage us to forecast that the recently discovered "easy-PACId" research strategy is suitable for constructing entomopathogenic-bacterium (EPB) strains producing and releasing single, harmless, non-ribosomal templated anti-microbial peptides with considerable drug, (probiotic)-candidate potential.
PubMed: 37760758
DOI: 10.3390/antibiotics12091462 -
Molecular Biology Reports Jun 2024Protease S (PrtS) from Photorhabdus laumondii belongs to the group of protealysin-like proteases (PLPs), which are understudied factors thought to play a role in the...
BACKGROUND
Protease S (PrtS) from Photorhabdus laumondii belongs to the group of protealysin-like proteases (PLPs), which are understudied factors thought to play a role in the interaction of bacteria with other organisms. Since P. laumondii is an insect pathogen and a nematode symbiont, the analysis of the biological functions of PLPs using the PrtS model provides novel data on diverse types of interactions between bacteria and hosts.
METHODS AND RESULTS
Recombinant PrtS was produced in Escherichia coli. Efficient inhibition of PrtS activity by photorin, a recently discovered emfourin-like protein inhibitor from P. laumondii, was demonstrated. The Galleria mellonella was utilized to examine the insect toxicity of PrtS and the impact of PrtS on hemolymph proteins in vitro. The insect toxicity of PrtS is reduced compared to protease homologues from non-pathogenic bacteria and is likely not essential for the infection process. However, using proteomic analysis, potential PrtS targets have been identified in the hemolymph.
CONCLUSIONS
The spectrum of identified proteins indicates that the function of PrtS is to modulate the insect immune response. Further studies of PLPs' biological role in the PrtS and P. laumondii model must clarify the details of PrtS interaction with the insect immune system during bacterial infection.
Topics: Animals; Photorhabdus; Moths; Peptide Hydrolases; Bacterial Proteins; Hemolymph; Proteomics; Recombinant Proteins; Escherichia coli
PubMed: 38824247
DOI: 10.1007/s11033-024-09654-8