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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 -
FEMS Microbiology Letters Mar 2016Photorhabdus (Enterobacteriaceae) bacteria are pathogenic to insects and mutualistic with entomopathogenic Heterorhabditis nematodes. Photorhabdus luminescens subsp....
Photorhabdus (Enterobacteriaceae) bacteria are pathogenic to insects and mutualistic with entomopathogenic Heterorhabditis nematodes. Photorhabdus luminescens subsp. akhurstii LN2, associated with Heterorhabditis indica LN2, shows nematicidal activity against H. bacteriophora H06 infective juveniles (IJs). In the present study, an rpoS mutant of P. luminescens LN2 was generated through allelic exchange to examine the effects of rpoS deletion on the nematicidal activity and nematode development. The results showed that P. luminescens LN2 required rpoS for nematicidal activity against H06 nematodes, normal IJ recovery and development of H. indica LN2, however, not for the bacterial colonization in LN2 and H06 IJs. This provides cues for further understanding the role of rpoS in the mutualistic association between entomopathogenic nematodes and their symbionts.
Topics: Animals; Antibiosis; Bacterial Proteins; Gene Deletion; Mutagenesis, Insertional; Mutation; Nematoda; Photorhabdus; Sigma Factor
PubMed: 26884480
DOI: 10.1093/femsle/fnw035 -
Acta Tropica Nov 2022Aedes aegypti and Aedes albopictus are important vectors for several arboviruses such as the dengue virus. The chemical control of Aedes spp., which is usually...
Aedes aegypti and Aedes albopictus are important vectors for several arboviruses such as the dengue virus. The chemical control of Aedes spp., which is usually implemented, affects both humans and the environment. The biological control of Aedes spp. with entomopathogenic bacteria such as Photorhabdus and Xenorhabdus may be an alternative method that can overcome such issues. This study aimed to isolate and identify Photorhabdus and Xenorhabdus bacteria from entomopathogenic nematodes (EPNs) collected in Thailand and evaluate their larvicidal properties in controlling A. aegypti and A. albopictus. Colony morphology and recA sequencing of the 118 symbiotic isolated bacteria indicated that most were P. luminescens subsp. akhurstii and X. stockiae with minor prevalence of P. luminescens subsp. hainanensis, P. asymbiotica subsp. australis, X. indica, X. griffiniae, X. japonica, X. thuongxuanensis, and X. eapokensis. The larvicidal bioassay with the third- and fourth-instar mosquito larvae suggested that a whole-cell suspension of X. griffiniae (bMSN3.3_TH) had the highest efficiency in eradicating A. aegypti and A. albopictus, with 90 ± 3.71% and 81 ± 2.13% mortality, respectively, after 96 h exposure. In contrast, 1% of ethyl acetate extracted from X. indica (bSNK8.5_TH) showed reduced mortality for A. aegypti of only 50 ± 3.66% after 96 h exposure. The results indicate that both X. griffiniae (bMSN3.3_TH) and X. indica (bSNK8.5_TH) could be used as biocontrol agents against Aedes larvae.
Topics: Aedes; Animals; Humans; Insecticides; Larva; Mosquito Vectors; Nematoda; Photorhabdus; Xenorhabdus
PubMed: 36030882
DOI: 10.1016/j.actatropica.2022.106668 -
International Journal of Systematic and... Mar 2019Two Gram-negative, rod-shaped, non-spore-forming bacteria, MEX20-17 and MEX47-22, were isolated from the digestive system of Heterorhabditis atacamensis and...
Photorhabdus khanii subsp. guanajuatensis subsp. nov., isolated from Heterorhabditis atacamensis, and Photorhabdus luminescens subsp. mexicana subsp. nov., isolated from Heterorhabditis mexicana entomopathogenic nematodes.
Two Gram-negative, rod-shaped, non-spore-forming bacteria, MEX20-17 and MEX47-22, were isolated from the digestive system of Heterorhabditis atacamensis and Heterorhabditis mexicana entomopathogenic nematodes, respectively. Their 16S rRNA gene sequences suggest that strains MEX20-17 and MEX47-22 belong to the γ-Proteobacteria and to the genus Photorhabdus. Deeper analyses using housekeeping-gene-based and whole-genome-based phylogenetic reconstruction suggest that MEX20-17 is closely related to Photorhabdus khanii and that MEX47-22 is closely related to Photorhabdus luminescens. Sequence similarity scores confirm these observations: MEX20-17 and P. khanii DSM 3369 share 98.9 % nucleotide sequence identity (NSI) of concatenated housekeeping genes, 70.4 % in silico DNA-DNA hybridization (isDDH) and 97 % orthologous average nucleotide identity (orthoANI); and MEX47-22 and P. luminescens ATCC 29999 share 98.9 % NSI, 70.6 % isDDH and 97 % orthoANI. Physiological characterization indicates that both strains differ from all validly described Photorhabdus species and from their more closely related taxa. We therefore propose to classify MEX20-17 and MEXT47-22 as new subspecies within P. khanii and P. luminescens, respectively. Hence, the following names are proposed for these strains: Photorhabdus khanii subsp. guanajuatensis subsp. nov. with the type strain MEX20-17 (=LMG 30372=CCOS 1191) and Photorhabdus luminescenssubsp. mexicana subsp. nov. with the type strain MEX47-22 (=LMG 30528=CCOS 1199). These propositions automatically create Photorhabdus khanii subsp. khanii subsp. nov. with DSM 3369 as the type strain (currently classified as P. khanii), and Photorhabdus luminescenssubsp. luminescenssubsp. nov. with ATCC 29999 as the type strain (currently classified as P. luminescens).
Topics: Animals; Bacterial Typing Techniques; Base Composition; DNA, Bacterial; Fatty Acids; Mexico; Nucleic Acid Hybridization; Photorhabdus; Phylogeny; RNA, Ribosomal, 16S; Rhabditoidea; Sequence Analysis, DNA; Soil
PubMed: 30688647
DOI: 10.1099/ijsem.0.003154 -
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 -
Current Topics in Microbiology and... 2017Bacterial communication via small diffusible molecules to mediate group-coordinated behaviour is commonly referred to as 'quorum sensing'. The prototypical quorum...
Bacterial communication via small diffusible molecules to mediate group-coordinated behaviour is commonly referred to as 'quorum sensing'. The prototypical quorum sensing system of Gram-negative bacteria consists of a LuxI-type autoinducer synthase that produces acyl-homoserine lactones (AHLs) as signals and a LuxR-type receptor that detects the AHLs to control expression of specific genes. However, many bacteria possess LuxR homologs but lack a cognate LuxI-type AHL-synthase. Those LuxR-type receptors are designated as 'LuxR orphans' or 'solos'. Entomopathogenic bacteria of the genus Photorhabdus all harbour a large number of LuxR solos, more than any other bacteria examined so far. Two novel quorum sensing systems were found to regulate cell clumping in Photorhabdus and therefore affect pathogenicity. In Photorhabdus luminescens and Photorhabdus temperata the LuxR solo PluR senses α-pyrones named 'photopyrones' instead of AHLs, which are produced by the pyrone synthase PpyS. In contrast, Photorhabdus asymbiotica, a closely related insect and human pathogen, has the PluR homolog PauR, which senses dialkylresorcinols produced by the DarABC pathway to regulate pathogenicity. All three Photorhabdus species harbour at least one LuxR solo with an intact AHL-binding motif, which might also allow sensing of exogenous AHLs. However, the majority of the LuxR solos in all Photorhabdus species have a PAS4 signal-binding domain. These receptors are assumed to detect eukaryotic compounds and are proposed to be involved in host sensing. Overall, because of the large number of LuxR solos they encode, bacteria of the genus Photorhabdus are ideal candidates to study and to identify novel bacterial communication networks.
Topics: Acyl-Butyrolactones; Bacterial Proteins; Gene Expression Regulation, Bacterial; Humans; Photorhabdus; Quorum Sensing; Repressor Proteins; Trans-Activators
PubMed: 27848037
DOI: 10.1007/82_2016_28 -
Trends in Microbiology Oct 2015Pathogenic bacteria encode virulent glycosyltransferases that conjugate various glycans onto substrate proteins via the N- or O-linkage. The HMW system in nontypeable... (Review)
Review
Pathogenic bacteria encode virulent glycosyltransferases that conjugate various glycans onto substrate proteins via the N- or O-linkage. The HMW system in nontypeable Haemophilus influenzae and the Pgl system in Campylobacter jejuni glycosylate bacterial surface or periplasmic proteins at the eukaryotic-like Asn-X-Ser/Thr motif. The NleB effector from enterobacteria mediates arginine GlcNAcylation of host death-domain proteins to block inflammation, representing an atypical N-glycosylation. The large clostridial cytotoxins and related glucosyltransferase toxins from Legionella and Photorhabdus monoglycosylate a serine/threonine or tyrosine in host Rho GTPase or elongation factor 1A (eEF1A). The emerging bacterial autotransporter heptosyltransferase (BAHT) family of heptosyltransferases also catalyses O-glycosylation and modifies autotransporters for adhesion to the host. These glycosylations, diverse in linkages and glycan structures, determine appropriate functioning of bacterial virulence factors or hijack host cellular processes in pathogenesis.
Topics: Animals; Bacterial Adhesion; Bacterial Proteins; Glycosylation; Glycosyltransferases; Humans
PubMed: 26433695
DOI: 10.1016/j.tim.2015.07.003 -
Toxins Oct 2016ExoU, a type III secretory toxin and major virulence factor with patatin-like phospholipase activity, is responsible for acute lung injury and sepsis in... (Review)
Review
ExoU, a type III secretory toxin and major virulence factor with patatin-like phospholipase activity, is responsible for acute lung injury and sepsis in immunocompromised patients. Through use of a recently updated bacterial genome database, protein sequences predicted to be homologous to ExoU were identified in 17 other species (, , , , , , , , , , , , , , and ) and 8 Gram-negative bacteria from three other genera (, , and ). In the alignment of the predicted primary amino acid sequences used for the phylogenetic analyses, both highly conserved and nonconserved parts of the toxin were discovered among the various species. Further comparative studies of the predicted ExoU homologs should provide us with more detailed information about the unique characteristics of the ExoU toxin.
Topics: Animals; Bacterial Proteins; Bacterial Toxins; Gram-Negative Bacteria; Humans; Molecular Chaperones; Phospholipases
PubMed: 27792159
DOI: 10.3390/toxins8110307 -
Journal of the Pediatric Infectious... Aug 2018Photorhabdus luminescens is a rare bacterium that causes human disease. In this report, we describe the case of a neonate with Photorhabdus luminescens bacteremia,... (Review)
Review
Photorhabdus luminescens is a rare bacterium that causes human disease. In this report, we describe the case of a neonate with Photorhabdus luminescens bacteremia, including clinical presentation and treatment; we also report a literature review of rare human diseases.
Topics: Anti-Bacterial Agents; Bacteremia; Ceftazidime; Female; Humans; Infant, Newborn; Neonatal Sepsis; Photorhabdus; Skin Diseases, Bacterial
PubMed: 30010886
DOI: 10.1093/jpids/piy064 -
Microbiology (Reading, England) May 2019Members of the Gram-negative bacterial genus Photorhabdus are all highly insect pathogenic and exist in an obligate symbiosis with the entomopathogenic nematode worm...
Members of the Gram-negative bacterial genus Photorhabdus are all highly insect pathogenic and exist in an obligate symbiosis with the entomopathogenic nematode worm Heterorhabditis. All members of the genus produce the small-molecule 3,5-dihydroxy-4-isopropyl-trans-stilbene (IPS) as part of their secondary metabolism. IPS is a multi-potent compound that has antimicrobial, antifungal, immunomodulatory and anti-cancer activities and also plays an important role in symbiosis with the nematode. In this study we have examined the response of Photorhabdus itself to exogenous ectopic addition of IPS at physiologically relevant concentrations. We observed that the bacteria had a measureable phenotypic response, which included a decrease in bioluminescence and pigment production. This was reflected in changes in its transcriptomic response, in which we reveal a reduction in transcript levels of genes relating to many fundamental cellular processes, such as translation and oxidative phosphorylation. Our observations suggest that IPS plays an important role in the biology of Photorhabdus bacteria, fulfilling roles in quorum sensing, antibiotic-competition advantage and maintenance of the symbiotic developmental cycle.
Topics: Bacterial Proteins; Gene Expression Regulation, Bacterial; Oxidative Phosphorylation; Photorhabdus; Quorum Sensing; Secondary Metabolism; Stilbenes
PubMed: 30882293
DOI: 10.1099/mic.0.000790