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Molecular Microbiology Aug 2010Fimbriae are adhesive organelles known to enable pathogens to colonize animal tissue, but little is known of their function in mutualistic symbioses. Photorhabdus...
Fimbriae are adhesive organelles known to enable pathogens to colonize animal tissue, but little is known of their function in mutualistic symbioses. Photorhabdus colonization of Heterorhabditis bacteriophora nematodes is essential for the pair's insect pathogenic lifestyle. Maternal nematodes acquire Photorhabdus symbionts as a persistent intestinal biofilm prior to transmission to infective juvenile (IJ) stage offspring developing inside the maternal body. Screening 8000 Photorhabdus mutants for defects in IJ colonization revealed that a single fimbrial locus, named mad for maternal adhesion defective, is essential. The mad genes encode a novel usher/chaperone assembled fimbria regulated by an ON/OFF invertible promoter switch. Adherent Photorhabdus cells in maternal nematode intestines had the switch ON opposite to the OFF orientation of most other cells. A ΔmadA mutant failed to adhere to maternal intestines and be transmitted to the IJs. Mad fimbriae were detected on TT01 phase ON cells but not on ΔmadA phase ON cells. Also required for transmission is madJ, predicted to encode a transcriptional activator related to GrlA. Expression of madA-K or madIJK restored the ability of madJ mutant to adhere. The Mad fimbriae were not required for insect pathogenesis, indicating the specialized function of Mad fimbriae for symbiosis.
Topics: Animals; Bacterial Adhesion; Biofilms; Fimbriae Proteins; Gastrointestinal Tract; Gene Deletion; Gene Expression Regulation, Bacterial; Genes, Bacterial; Genetic Loci; Multigene Family; Operon; Photorhabdus; Promoter Regions, Genetic; Rhabditoidea; Symbiosis
PubMed: 20572934
DOI: 10.1111/j.1365-2958.2010.07270.x -
Systematic and Applied Microbiology May 2016Photorhabdus is a genus of Gram-negative bacteria belonging to the Enterobacteriaceae family. In addition to forming a mutualistic relationship with the...
Photorhabdus is a genus of Gram-negative bacteria belonging to the Enterobacteriaceae family. In addition to forming a mutualistic relationship with the Heterorhabditidae family of nematodes, these bacteria are the causal agent of insect mortality during nematode infection, and are commonly used as biocontrol agents against pest insects in managed ecosystems. There are three described species of Photorhabdus; Photorhabdus luminescens and Photorhabdus temperata, which are strictly entomopathogens, and Photorhabdus asymbiotica, which has been isolated from wound infections in humans. While there has been extensive research on its virulence mechanisms, the evolution of virulence in Photorhabdus has not previously been investigated within a phylogenetic context. To investigate how virulence has evolved in this genus, we first reconstructed the phylogenetic relationships among 18 strains representing each of the main taxonomic lineages in the genus. Bacterial cells were injected into Galleria mellonella and Tenebrio molitor larvae, and the LT50 was calculated for each strain. These values were mapped onto the phylogeny using ancestral character reconstruction methods. With few exceptions, we found that the general trend of Photorhabdus evolution is one of increasing virulence. We also explored the relationship between virulence and Photorhabdus cell types and growth rates. Although we found no correlation between cell type and virulence, there was a strong correlation between virulence and growth rates in T. molitor. A better understanding of the origin and maintenance of virulence in this bacterium will aid in unraveling the mechanisms of the Heterorhabditis-Photorhabdus complex, resulting in the selection of more effective nematode-bacterium complexes for biocontrol.
Topics: Animals; Base Sequence; Biological Control Agents; DNA Gyrase; DNA, Bacterial; Moths; Photorhabdus; Phylogeny; RNA, Ribosomal, 16S; Rhabditoidea; Sequence Alignment; Sequence Analysis, DNA; Tenebrio; Virulence
PubMed: 27020955
DOI: 10.1016/j.syapm.2016.02.003 -
The Journal of Antibiotics Aug 2016Photorhabdus luminescens is a bioluminescent entomopathogenic bacterium that undergoes phenotypic variation and lives in mutualistic association with nematodes of the...
Photorhabdus luminescens is a bioluminescent entomopathogenic bacterium that undergoes phenotypic variation and lives in mutualistic association with nematodes of the family Heterorhabditidae. The pair infects and kills insects, and during their coordinated lifecycle, the bacteria produce an assortment of specialized metabolites to regulate its mutualistic and pathogenic roles. As part of our search for new specialized metabolites from the Photorhabdus genus, we examined organic extracts from P. luminescens grown in an amino-acid-rich medium based on the free amino-acid levels found in the circulatory fluid of its common insect prey, the Galleria mellonella larva. Reversed-phase HPLC/UV/MS-guided fractionation of the culture extracts led to the identification of two new pyrazinone metabolites, lumizinones A (1) and B (2), together with two N-acetyl dipeptides (3 and 4). The lumizinones were produced only in the phenotypic variant associated with nematode development and insect pathogenesis. Their chemical structures were elucidated by analysis of 1D and 2D NMR and high-resolution ESI-QTOF-MS spectral data. The absolute configurations of the amino acids in 3 and 4 were determined by Marfey's analysis. Compounds 1-4 were evaluated for their calpain protease inhibitory activity, and lumizinone A (1) showed inhibition with an IC50 (half-maximal inhibitory concentration) value of 3.9 μm.
Topics: Amino Acids; Animals; Chromatography, High Pressure Liquid; Inhibitory Concentration 50; Lepidoptera; Magnetic Resonance Spectroscopy; Mass Spectrometry; Photorhabdus; Protease Inhibitors; Pyrazines; Spectrometry, Mass, Electrospray Ionization
PubMed: 27353165
DOI: 10.1038/ja.2016.79 -
Journal of Invertebrate Pathology Sep 2022Phurealipids (Photorhabdus urea lipids) are synthesized from Photorhabdus bacteria that are symbiotic to entomopathogenic nematodes. Their chemical structures are...
Phurealipids (Photorhabdus urea lipids) are synthesized from Photorhabdus bacteria that are symbiotic to entomopathogenic nematodes. Their chemical structures are similar to that of juvenile hormone (JH) and have been suspected to mimic JH signaling in immunity and the development of insects. This study investigated the physiological roles of phurealipids with respect to their contribution to bacterial pathogenicity using four natural (HB13, HB69, HB416, and HB421) and one derivative (HB27) compound. First, phurealipids like JH suppressed insect immune responses. Overall, phurealipids showed JH like immunosuppressive behavior in a lepidopteran insect Spodoptera exigua larvae. More specifically, phurealipids significantly suppressed the hemocyte spreading behavior which is a key immune response upon immune challenge. Interestingly, the methyl urea derivatives (HB13, HB27, and HB69) were more potent than the unmethylated forms (HB416 and HB421). The inhibitory activity of phurealipids prevented the cellular immune response measured by hemocytic nodule formation in response to the bacterial challenge. Phurealipids also suppressed the expression of cecropin and gallerimycin, which are two highly inducible antimicrobial peptides, in S. exigua upon immune challenge. The immunosuppressive activity of the phurealipids significantly enhanced the bacterial pathogenicity of Bacillus thuringiensis against S. exigua. Second, phurealipids like JH prevented insect metamorphosis. Especially, the methylated urea derivatives of the phurealipids showed the JH-like function by inducing the expression of S. exigua Kr-h1, a transcriptional factor. At the pupal stage, exhibiting the lowest expression of Kr-h1, phurealipid treatments elevated the expression level of Kr-h1 and delayed the pupa-to-adult metamorphosis. These results suggest that phurealipids play crucial roles in Photorhabdus pathogenicity by suppressing host immune defenses and delaying host metamorphosis.
Topics: Animals; Insect Proteins; Insecta; Juvenile Hormones; Larva; Lipid Metabolism; Lipids; Photorhabdus; Pupa; Urea
PubMed: 35850258
DOI: 10.1016/j.jip.2022.107799 -
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 -
Current Topics in Microbiology and... 2017The death of the insect host is an essential part of the life cycle of Photorhabdus, and as a result, this bacterium comes equipped with a dazzlingly large array of...
The death of the insect host is an essential part of the life cycle of Photorhabdus, and as a result, this bacterium comes equipped with a dazzlingly large array of toxins and virulence factors that ensure rapid insect death. Elucidation of the key players in insect infection and mortality has therefore proved difficult using traditional microbiological techniques such as individual gene knockouts due to the high level of functional redundancy displayed by Photorhabdus virulence factors. Thus, knockout of any individual toxin gene may serve to delay time to death but not to render the bacteria avirulent due to the continued presence of an array of other toxins and virulence factors in the single-gene mutant. This functional redundancy had led to the necessary development of an array of techniques and new model systems for identifying and dissecting apart the action of anti-insect effectors produced by Photorhabdus. These have been pivotal in both the identification of new toxins and virulence factors and in ascribing functions to them. These techniques have gone on to prove valuable in pathogenic bacteria other than Photorhabdus and are likely to be useful in many others.
Topics: Bacterial Toxins; Gene Knockout Techniques; Photorhabdus; Virulence Factors
PubMed: 28091931
DOI: 10.1007/82_2016_51 -
International Journal of Systematic and... May 2014The bacterial symbionts SF41T and SF783 were isolated from populations of the insect pathogenic nematode Heterorhabditis zealandica collected in South Africa. Both...
The bacterial symbionts SF41T and SF783 were isolated from populations of the insect pathogenic nematode Heterorhabditis zealandica collected in South Africa. Both strains were closely related to strain Q614 isolated from a population of Heterorhabditis sp. collected from soil in Australia in the 1980s. Sequence analysis based on a multigene approach, DNA-DNA hybridization data and phenotypic traits showed that strains SF41T, SF783 and Q614 belong to the same species of the genus Photorhabdus with Photorhabdus temperata subsp. cinerea as the most closely related taxon (DNA-DNA hybridization value of 68%). Moreover, the phylogenetic position of Photorhabdus temperata subsp. cinerea DSM 19724T initially determined using the gyrB sequences, was reconsidered in the light of the data obtained by our multigene approach and DNA-DNA hybridization experiments. Strains SF41T, SF783 and Q614 represent a novel species of the genus Photorhabdus, for which the name Photorhabdus heterorhabditis sp. nov. is proposed (type strain SF41T=ATCC BAA-2479T=DSM 25263T).
Topics: Animals; Bacterial Typing Techniques; Base Sequence; DNA, Bacterial; Genes, Bacterial; Insecta; Molecular Sequence Data; Nucleic Acid Hybridization; Photorhabdus; Phylogeny; RNA, Ribosomal, 16S; Rhabditoidea; Sequence Analysis, DNA; South Africa; Symbiosis
PubMed: 24478206
DOI: 10.1099/ijs.0.059840-0 -
Toxicon : Official Journal of the... Jun 2016Photorhabdus bacteria live in symbiosis with entomopathogenic nematodes. The nematodes invade insect larvae, where they release the bacteria, which then produce toxins...
Photorhabdus bacteria live in symbiosis with entomopathogenic nematodes. The nematodes invade insect larvae, where they release the bacteria, which then produce toxins to kill the insects. Recently, the molecular mechanisms of some toxins from Photorhabdus luminescens and asymbiotica have been elucidated, showing that GTP-binding proteins of the Rho family are targets. The tripartite Tc toxin PTC5 from P. luminescens activates Rho proteins by ADP-ribosylation of a glutamine residue, which is involved in GTP hydrolysis, while PaTox from Photorhabdus asymbiotica inhibits the activity of GTPases by N-acetyl-glucosaminylation at tyrosine residues and activates Rho proteins indirectly by deamidation of heterotrimeric G proteins.
Topics: Animals; Bacterial Toxins; Insecta; Larva; Models, Molecular; Photorhabdus; Protein Domains; rho GTP-Binding Proteins
PubMed: 26026623
DOI: 10.1016/j.toxicon.2015.05.017 -
Nucleic Acids Research Mar 2015Precise and fluent genetic manipulation is still limited to only a few prokaryotes. Ideally the highly advanced technologies available in Escherichia coli could be...
Precise and fluent genetic manipulation is still limited to only a few prokaryotes. Ideally the highly advanced technologies available in Escherichia coli could be broadly applied. Our efforts to apply lambda Red technology, widely termed 'recombineering', in Photorhabdus and Xenorhabdus yielded only limited success. Consequently we explored the properties of an endogenous Photorhabdus luminescens lambda Red-like operon, Plu2934/Plu2935/Plu2936. Bioinformatic and functional tests indicate that Plu2936 is a 5'-3' exonuclease equivalent to Redα and Plu2935 is a single strand annealing protein equivalent to Redβ. Plu2934 dramatically enhanced recombineering efficiency. Results from bioinformatic analysis and recombineering assays suggest that Plu2934 may be functionally equivalent to Redγ, which inhibits the major endogenous E. coli nuclease, RecBCD. The recombineering utility of Plu2934/Plu2935/Plu2936 was demonstrated by engineering Photorhabdus and Xenorhabdus genomes, including the activation of the 49-kb non-ribosomal peptide synthase (NRPS) gene cluster plu2670 by insertion of a tetracycline inducible promoter. After tetracycline induction, novel secondary metabolites were identified. Our work unlocks the potential for bioprospecting and functional genomics in the Photorhabdus, Xenorhabdus and related genomes.
Topics: Amino Acid Sequence; Bacterial Proteins; Bacteriophage lambda; DNA, Bacterial; Escherichia coli; Exodeoxyribonuclease V; Genetic Engineering; Genome, Bacterial; Genomics; Molecular Sequence Data; Multigene Family; Operon; Photorhabdus; Plasmids; Recombination, Genetic; Sequence Homology, Amino Acid; Xenorhabdus
PubMed: 25539914
DOI: 10.1093/nar/gku1336 -
Science China. Life Sciences Mar 2022The extracellular contractile injection systems (eCISs) are encoded in the genomes of a large number of bacteria and archaea. We have previously characterized the...
The extracellular contractile injection systems (eCISs) are encoded in the genomes of a large number of bacteria and archaea. We have previously characterized the overall structure of Photorhabdus Virulence Cassette (PVC), a typical member of the eCIS family. PVC resembles the contractile tail of bacteriophages and exerts its action by the contraction of outer sheath and injection of inner tube plus central spike. Nevertheless, the biological function of PVC effectors and the mechanism of effector translocation are still lacking. By combining cryo-electron microscopy and functional experiments, here we show that the PVC effectors Pdp1 (a new family of widespread dNTP pyrophosphatase effector in eCIS) and Pnf (a deamidase effector) are loaded inside the inner tube lumen in a "Peas in the Pod" mode. Moreover, we observe that Pdp1 and Pnf can be directly injected into J774A.1 murine macrophage and kill the target cells by disrupting the dNTP pools and actin cytoskeleton formation, respectively. Our results provide direct evidence of how PVC cargoes are loaded and delivered directly into mammalian macrophages.
Topics: Cryoelectron Microscopy; HEK293 Cells; HeLa Cells; Humans; Mutagenesis, Site-Directed; Open Reading Frames; Photorhabdus; Pyrophosphatases; Virulence; rho GTP-Binding Proteins
PubMed: 34185241
DOI: 10.1007/s11427-021-1955-4