Journal of invertebrate pathology最新文献

{"title":"The combined effect of herbicide and Bacillus thuringiensis exposure delays development in the red flour beetle","authors":"Maria Luigia Vommaro ,&nbsp;Ana Korša ,&nbsp;Ana Sofia Lindeza ,&nbsp;Anita Giglio ,&nbsp;Joachim Kurtz","doi":"10.1016/j.jip.2024.108227","DOIUrl":"10.1016/j.jip.2024.108227","url":null,"abstract":"<div><div>The use of herbicides and their long persistence in the environment have raised concerns about potential harm to ecosystems and human health. However, there is a gap in the knowledge regarding the effects of continuous exposure to residues or admitted field doses on non-target organisms such as insects that inhabit croplands and play key ecological roles. Furthermore, the potential impact of this exposure on host-pathogen interactions remains largely unstudied. This study adopted an eco-immunological perspective, investigating the influence of herbicides on an organism’s interaction with natural pathogens. The impact of this combination of multiple stressors was studied in larvae of the red flour beetle, <em>Tribolium castaneum</em> Herbst, 1797, previously treated with a pendimethalin-based commercial formulation (PND) and exposed to the natural entomopathogen <em>Bacillus thuringiensis</em> (1x10⁹, 1x10¹⁰ cells/mL)<em>.</em> The effects of three PND concentrations (i.e. a recommended field rate, a soil contaminant concentration and the maximum residue limit admitted in grain in EU countries: 4L/ha, 13 and 0.05 ppm, respectively) on life history traits such as developmental time, pupation rate and survival rate and the expression levels of antimicrobial peptides (AMPs) were assessed. The results showed that even at doses considered safe for human consumption or field application, exposure to PND had an impact on beetle larvae, affecting their vulnerability to <em>B. thuringiensis</em>. The combined experience of exposure to PND and <em>B. thuringiensis</em> at the larval stage resulted in a delay of larval development, a reduction in the number of pupae and emerging adults, and alterations in their body condition. Moreover, changes in the expression levels of the analysed AMPs, including Attacin 1, Defensin 2 and Coleoptericin 2, were recorded as markers for immune activity against the bacterium. The findings of this study highlight the general need for further studies on the effects of commonly used herbicides on the physiology of non-target organisms and on host-pathogen interactions at the community level. Additionally, there is a need for the establishment of revised residual levels that are deemed non-toxic to soil organisms and humans.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108227"},"PeriodicalIF":3.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142545942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"To be a good killer: Evaluation of morphometry and nematodes-bacteria complex effect on entomopathogenic nematodes virulence against wireworms","authors":"Andrea Chacon-Hurtado ,&nbsp;Fanny Ruhland ,&nbsp;Salimata Drabo ,&nbsp;Thibaut Smeets ,&nbsp;Brice Checconi ,&nbsp;Raquel Campos-Herrera ,&nbsp;François J. Verheggen","doi":"10.1016/j.jip.2024.108231","DOIUrl":"10.1016/j.jip.2024.108231","url":null,"abstract":"<div><div>Entomopathogenic nematodes (EPNs) have emerged as a promising tool for controlling soil-dwelling crop pests. However, their efficacy varies according to EPN populations and targeted hosts. Wireworms are polyphagous insects causing significant crop losses, especially since the ban on pesticides previously used for their control. They are highly resistant to EPN populations and require high number of infective juveniles (IJs) to achieve optimal mortality rates. In this research, we collected and compared the virulence of 16 EPN populations, of foreign origin, purchased or collected from wireworms infested fields. Then, we have tested two hypotheses: (i) smaller nematodes induce heightened mortality rates against wireworms; (ii) virulence levels can be linked to nematodes-bacteria complex. Mortality rates scaled from three to 43 % after 56 days of continuous exposure across the 16 tested EPN populations (<em>Heterorhabditis</em> spp. and <em>Steinernema</em> spp.). Morphometric analysis of IJs revealed both intra- and interspecific variations in length and diameter among populations. Interestingly, while EPN length influence mortality at three days post-inoculation. We found leaner IJs (&lt; 25 µm) to induce higher mortality rates at 56 days post-inoculation. To better determine the structure and dimensions of the primary entry routes utilized by EPNs, we provide optical microscope micrographs of wireworm <em>Agriotes</em> spp. spiracle, anal sclerotized coating anus and anal muscles. Symbiotic bacteria of each EPN population were identified, and a biochemical characterization was performed using Analytical Profile Index tests. The symbiotic bacteria belong to the species <em>Photorhabdus antumapuensis, P. laumondii</em> subsp<em>. laumondii</em>, <em>P. thracensis, Xenorhabdus bovienii</em> and <em>X. nematophila</em>. Bacteria biochemical profiles did not reflect the differences in virulence of nematodes-bacteria complex against wireworms. These findings highlight the importance of considering EPN morphometry and intraspecific variability in designing applications to control wireworms.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108231"},"PeriodicalIF":3.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142622269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metacollinia emscheri n. sp., a novel sanguicolous apostome ciliate of freshwater amphipods (Gammarus spp.)","authors":"Sebastian Prati ,&nbsp;Sonja Rückert ,&nbsp;Daniel S. Grabner ,&nbsp;Bernd Sures ,&nbsp;Jamie Bojko","doi":"10.1016/j.jip.2024.108224","DOIUrl":"10.1016/j.jip.2024.108224","url":null,"abstract":"<div><div>We describe a novel sanguicolous parasitic ciliate, <em>Metacollinia emscheri</em> n. sp., found in the freshwater amphipods <em>Gammarus pulex</em> and <em>G. fossarum</em>. This ciliate infected 8.05 % of the amphipods collected in a German stream catchment, the Boye, a tributary of the river Emscher. The ciliate showed morphological characteristics fitting the genus <em>Metacollinia</em>. Different life stages of variable size occurred simultaneously in the hemocoel throughout the hosts’ body. The tomont had 40–47 slightly spiraled kineties, a non-ciliated cortical band, a large macronucleus, and contractile vacuoles arranged in rows or scattered throughout the cytoplasm. The protomites/tomites with nine somatic kineties presented evidence of the buccal kineties x, y, and z reminiscent of those of the order Foettingeriida. Phylogenetic analyses of the 18S rRNA and COI regions confirm the ciliate placement in the Collinidae and a close relatedness to the type species of the genus <em>Metacollinia</em>, <em>Metacollinia luciensis</em>.</div><div>We formally describe this new parasite as <em>Metacollinia emscheri</em> n. sp. using pathological, morphological, and nuclear/mitochondrial genetic data. The systemic infections observed in histological preparations and the pathogenicity of <em>Metacollinia emscheri</em> n. sp. suggest that this parasite might influence host population dynamics. Given the ecological importance of amphipods as keystone species in freshwater ecosystems, an outbreak of this parasite might indirectly impact ecosystem functioning.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108224"},"PeriodicalIF":3.6,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142502200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ferroptotic cyanobacteria as biocontrol agent of the southern house mosquito Culex quinquefasciatus","authors":"Antonella Cuniolo ,&nbsp;María Victoria Martin ,&nbsp;Corina M Berón","doi":"10.1016/j.jip.2024.108225","DOIUrl":"10.1016/j.jip.2024.108225","url":null,"abstract":"<div><div><em>Culex quinquefasciatus</em> is a hematophagous mosquito, widely distributed around the world, that plays a crucial role in public and veterinary health. As an efficient vector of etiological agents, it exhibits a marked preference for urban environments and human blood. Despite advances in mosquito-borne disease control, managing mosquito populations remains an economically efficient and safe strategy to reduce the impact of epidemic outbreaks. However, achieving this goal requires ecologically acceptable tools that ensure sustainability and minimize adverse environmental impacts. In the present work, we investigated the effect of a non-toxigenic model cyanobacterium on <em>Cx. quinquefasciatus</em> larvae through regulated cell death. We observed that heat stress treatment of <em>Synechocystis</em> PCC 6803 inducing ferroptosis, results in larval lipid oxidation, leading to their death. This effect can be mitigated by rearing larvae in an environment containing canonical inhibitors of ferroptosis, such as ferrostatin 1, or antioxidants, like glutathione and ascorbic acid. Furthermore, larval cell death induced by ferroptotic cyanobacteria is closely linked to oxidative dysregulation and lipid peroxidation, both hallmarks of ferroptosis. Moreover, while ferroptotic <em>Synechocystis</em> significantly affects larval development, it does not influence oviposition site selection by gravid females.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108225"},"PeriodicalIF":3.6,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142502202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study on the role of RPL23 gene in active immunity of termite Reticulitermes chinensis against Metarhizium anisopliae","authors":"Shuxin Yu ,&nbsp;Ali Hassan ,&nbsp;Nasir Mehmood ,&nbsp;Wei Zhou ,&nbsp;Taqi Raza ,&nbsp;Qiuying Huang","doi":"10.1016/j.jip.2024.108226","DOIUrl":"10.1016/j.jip.2024.108226","url":null,"abstract":"<div><div>Ribosomal proteins are considered to be involved in the immunity of different animals against pathogens. The protein level of RPL23 increased after fungal infection in termites, but how it influence active immunity in termites is unknown. The role of <em>RPL23</em> gene was studied to evaluate its impact on active immunity of termite <em>Reticulitermes chinensis</em> against entomopathogenic fungus (EPF) <em>Metarhizium anisopliae</em>. The <em>RPL23</em> gene fragment (414 bp) was cloned and phylogenetic analysis revealed that it’s very close to termite <em>Coptotermes formosanus</em>. Expression of <em>RPL23</em> gene was significantly higher in abdomen as compared to thorax and head. Silencing <em>RPL23</em> gene had no significant impact on the frequency and time of allogrooming towards fungus exposed termites from nestmates, which showed that nestmates acquired spores from infected termites through allogrooming. Expression of immune genes (<em>GNBP1</em>, <em>GNBP2</em> and phenoloxidase) and apoptosis related genes (<em>TNF-α,</em> caspase 1, caspase 3 and caspase 8) decreased significantly in nestmates of fungus-treated termites after silencing of <em>RPL23</em> gene as compared to control. Antifungal activity and survival of <em>RPL23</em> silenced nestmates of fungus-treated termites also decreased. To sum up, this study found that silencing of <em>RPL23</em> gene broke the active immunity against <em>M. anisopliae</em> infection, reduced the antifungal activity of termites, weakened cell apoptosis, and led to increased mortality of termites, which may help to find a potential alternative for chemical insecticides to control termites.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108226"},"PeriodicalIF":3.6,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142502201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Damage to the host cadaver, simulating the effects of scavenging, differentially affects fitness of entomopathogenic nematode species","authors":"Maria D. Cassells ,&nbsp;Niamh Treanor ,&nbsp;Emigdio Jordán Muñoz-Adalia ,&nbsp;Christine T. Griffin","doi":"10.1016/j.jip.2024.108217","DOIUrl":"10.1016/j.jip.2024.108217","url":null,"abstract":"<div><div>Insect cadavers infected by entomopathogenic nematodes (EPN) are defended against scavengers by chemical mechanisms and other means. Despite these defences, the cadaver may be bitten before being rejected. In this study, we investigated the effect of damage to the cadaver cuticle on the fitness of nematodes (<em>Heterorhabditis downesi Stock, Griffin &amp; Burnell</em> or <em>Steinernema feltiae Filipjev</em>) developing inside. We first quantified the severity of scavenger damage to EPN-infected <em>Galleria mellonella</em> Linnaeus cadavers in the field, and separately, with crickets <em>(Gryllus bimaculatus</em> De Geer) in the laboratory. In both field and laboratory, EPN-infected cadavers suffered less damage than freeze-killed controls, and damage consisted mainly of small lesions to the cuticle. In further experiments, scavenging damage was simulated shortly after death of infected cadavers by piercing the cuticle 0, 1, 3 or 5 times and incubating in moist (100% relative humidity (RH)) or dry (60–70% RH) conditions. The greater the level of damage, the greater the loss of moisture from the cadaver (estimated by weight loss), and this was exacerbated in dry conditions. The number of infective juveniles (IJs) emerging from <em>H. downesi-</em>infected cadavers was significantly reduced by damage, especially in dry conditions. In addition, emerging IJs were progressively smaller with increasing damage. For this species, the number of IJs was negatively correlated with moisture loss, indicating that the reduction in fitness was mediated by desiccation. For <em>S. feltiae,</em> damage impacted IJ number to a lesser extent and size was not affected. The reduction in numbers was not explained by moisture loss, indicating that for <em>S. feltiae</em>, some factor other than desiccation (perhaps competition with opportunistic microbes) impacts the nematodes when the cuticle is damaged. The greater vulnerability of <em>H. downesi,</em> compared to <em>S. feltiae,</em> to scavenger damage to the host cadaver may be due to its longer developmental time in the host resulting in longer exposure to damaging conditions. In conclusion, damage simulating biting by scavengers impacts the fitness of EPN, with the effect depending on nematode species, environmental conditions and the extent of damage. These findings have implications for the success of field application of EPN in infected cadavers.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108217"},"PeriodicalIF":3.6,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142467749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chitinase and proteinase K treatments enhance the DNA yield of microsporidium Ecytonucleospora hepatopenaei spores","authors":"Xiao-Meng Guo ,&nbsp;Wen Gao ,&nbsp;Hai-Liang Wang ,&nbsp;Prapatsorn Wongkhaluang ,&nbsp;Suparat Taengchaiyaphum ,&nbsp;Guo-Si Xie ,&nbsp;Chen Li ,&nbsp;Ruo-Heng Zhao ,&nbsp;Kallaya Sritunyalucksana ,&nbsp;Jie Huang","doi":"10.1016/j.jip.2024.108222","DOIUrl":"10.1016/j.jip.2024.108222","url":null,"abstract":"<div><div>Microsporidium <em>Ecytonucleospora hepatopenaei</em> (EHP) spores were purified from the hepatopancreas of <em>Penaeus vannamei</em> infected with EHP by percoll density gradient centrifugation and differential centrifugation. The EHP spores contain a thick chitin wall and might not rupture using the routine DNA extraction protocol. In this study, three enzymes were used, including chitinase, proteinase K, and DNase I. Chitinase or proteinase K digestions caused weakened fluorescence of chitin showing by a blurred edge of EHP spores stained with calcofluor white under a fluorescence microscope. Different combinations of these enzymes followed by DNA extraction with phenol–chloroform from EHP spores showed significant increases in the copy number of the EHP SSU gene per spore. The combination of the chitinase and proteinase K treatments resulted 4.46 ± 1.07 copies/spore detected, which is 31.6 ± 20.7 folds of no treatment groups, accounting to (55.7 ± 13.4)% of the total copies of the gene in the spore. The additional treatment with chitinase to the conventional extraction protocol with a proteinase K digestion step for feces and hepatopancreas samples of <em>P. vannamei</em> resulted in a significant difference in EHP copies in the DNA of (83.8 ± 64.1)% and (55.3 ± 88.0)% increases. The study proved that chitinase and proteinase K treatment enhance the DNA extraction from microsporidian spores resulting in high yield.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108222"},"PeriodicalIF":3.6,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142467751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An alphabaculovirus from the zebra caterpillar, Melanchra picta Harris, is an isolate of species Alphabaculovirus maconfiguratae","authors":"Robert L. Harrison,&nbsp;Charlotte B. Francoeur,&nbsp;Daniel L. Rowley","doi":"10.1016/j.jip.2024.108220","DOIUrl":"10.1016/j.jip.2024.108220","url":null,"abstract":"<div><div>A baculovirus had been previously identified in larvae of the zebra caterpillar, <em>Melanchra</em> (formerly <em>Ceramica</em>) <em>picta</em> Harris. To further characterize this virus, two isolates, Melanchra picta nucleopolyhedrovirus-185 (MepiNPV-185) and MepiNPV-600, were fully sequenced. Analysis of the genome sequences revealed that both isolates are members of alphabaculovirus species <em>Alphabaculovirus maconfiguratae</em>, along with alphabaculoviruses of the bertha armyworm, <em>Mamestra configurata</em> Walker. MepiNPV-600 displayed relatively low virulence against larvae of <em>Trichoplusia ni</em> Hübner in bioassays compared to other <em>T. ni</em>-pathogenic alphabaculoviruses. MepiNPV likely arose from a cross-species transfer between <em>M. configurata</em> and <em>M. picta</em> larvae, which often occur together.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108220"},"PeriodicalIF":3.6,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nosema ceranae infection reduces the fat body lipid reserves in the honeybee Apis mellifera","authors":"Juliette Gilbert ,&nbsp;Laurianne Paris ,&nbsp;Aurore Dubuffet,&nbsp;Catherine Texier,&nbsp;Frédéric Delbac,&nbsp;Marie Diogon","doi":"10.1016/j.jip.2024.108218","DOIUrl":"10.1016/j.jip.2024.108218","url":null,"abstract":"<div><div><em>Nosema ceranae</em> is an intestinal parasite frequently found in <em>Apis mellifera</em> colonies. This parasite belongs to Microsporidia, a group of obligate intracellular parasites known to be strongly dependent on their host for energy and resources. Previous studies have shown that <em>N. ceranae</em> could alter several metabolic pathways, including those involved in the nutrient storage. To explore the impact of <em>N. ceranae</em> on the fat body reserves, newly emerged summer bees were experimentally infected, and we measured (1) the lipid percentage of the abdominal fat body at 2-, 7- and 14-days post-inoculation (p.i.) using diethyl ether lipid extraction, (2) the triglyceride and protein concentrations by spectrophotometric assay methods, and (3) the amount of intracellular lipid droplets in trophocytes at 14- and 21-days p.i. using Nile Red staining. Comparing the three methods used to evaluate lipid stores, our data revealed that Nile Red staining seemed to be the simplest, fastest and reliable method. Our results first revealed that the percentage of fat body lipids significantly decreased in infected bees at D14 p.i. The protein stores did not seem to be affected by the infection, while triglyceride concentration was reduced by 30% and lipid droplet amount by 50% at D14 p.i. Finally, a similar decrease in lipid droplet reserves in response to <em>N. ceranae</em> infection was observed in bees collected in fall.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108218"},"PeriodicalIF":3.6,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142406503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Suppression of a transcriptional regulator, HexA, is essential for triggering the bacterial virulence of the entomopathogen, Xenorhabdus hominickii","authors":"Gahyeon Jin ,&nbsp;Ji-Seon Jeong ,&nbsp;Il-Hwan Kim ,&nbsp;Yonggyun Kim","doi":"10.1016/j.jip.2024.108219","DOIUrl":"10.1016/j.jip.2024.108219","url":null,"abstract":"<div><div>A nematode-symbiotic bacterium, <em>Xenorhabdus hominickii</em>, exhibits two distinct lifestyles. Upon infection of its host nematode into a target insect, <em>X. hominickii</em> is released into the insect hemocoel and becomes pathogenic. This study examines the critical transformation in bacterial life forms concerning the activity of a transcriptional regulator, HexA. When <em>X. hominickii</em> was cultured in tryptic soy broth, <em>HexA</em> was expressed during the stationary phase of bacterial growth. Conversely, <em>HexA</em> was expressed in the early growth stage within the insect host, <em>Spodoptera exigua</em>, when infected with <em>X. hominickii</em>. The transient expression of <em>HexA</em> was succeeded by the expression of another transcriptional regulator, <em>Lrp</em>, which led to the production of bacterial virulent factors. Expression of <em>HexA</em> was manipulated by replacing its promoter with an inducible promoter controlled by the inducer, <span>l</span>-arabinose. In the absence of the inducer, the mutant bacteria expressed <em>HexA</em> at a low level, resulting in a bacterial culture broth that was more effective at suppressing insect immune responses than the wild type. When the inducer was added, <em>HexA</em> was expressed at high levels, rendering the culture broth ineffective in immunosuppression. Interestingly, expression of <em>HexA</em> inhibited the expression of another transcriptional regulator, <em>Lrp</em>, which in turn induced the expression of a non-ribosomal peptide synthetase, <em>gxpS</em>, leading to the production of an immunosuppressive metabolite, GXP. Suppression of <em>HexA</em> expression in mutant bacteria augmented GXP levels in secondary metabolites. This indicates that infection of <em>X. hominickii</em> into the insect host represses <em>HexA</em> expression and upregulates <em>Lrp</em> expression, leading to GXP production. The GXP metabolites inhibit insect immunity, thus protecting the bacteria-nematode complex. Therefore, the suppression of <em>HexA</em> expression in the insect hemocoel is crucial for the bacteria’s transition from a symbiotic to a pathogenic life form.</div></div>","PeriodicalId":16296,"journal":{"name":"Journal of invertebrate pathology","volume":"207 ","pages":"Article 108219"},"PeriodicalIF":3.6,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142406504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}