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The Entomopathogenic Bacterial Endosymbionts Xenorhabdus and Photorhabdus: Convergent Lifestyles from Divergent Genomes  [PDF]
John M. Chaston, Garret Suen, Sarah L. Tucker, Aaron W. Andersen, Archna Bhasin, Edna Bode, Helge B. Bode, Alexander O. Brachmann, Charles E. Cowles, Kimberly N. Cowles, Creg Darby, Limaris de Léon, Kevin Drace, Zijin Du, Alain Givaudan, Erin E. Herbert Tran, Kelsea A. Jewell, Jennifer J. Knack, Karina C. Krasomil-Osterfeld, Ryan Kukor, Anne Lanois, Phil Latreille, Nancy K. Leimgruber, Carolyn M. Lipke, Renyi Liu, Xiaojun Lu, Eric C. Martens, Pradeep R. Marri, Claudine Médigue, Megan L. Menard, Nancy M. Miller, Nydia Morales-Soto, Stacie Norton, Jean-Claude Ogier, Samantha S. Orchard, Dongjin Park, Youngjin Park, Barbara A. Qurollo, Darby Renneckar Sugar, Gregory R. Richards, Zoé Rouy, Brad Slominski, Kathryn Slominski, Holly Snyder, Brian C. Tjaden, Ransome van der Hoeven, Roy D. Welch, Cathy Wheeler, Bosong Xiang, Brad Barbazuk, Sophie Gaudriault, Brad Goodner, Steven C. Slater, Steven Forst, Barry S. Goldman, Heidi Goodrich-Blair
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0027909
Abstract: Members of the genus Xenorhabdus are entomopathogenic bacteria that associate with nematodes. The nematode-bacteria pair infects and kills insects, with both partners contributing to insect pathogenesis and the bacteria providing nutrition to the nematode from available insect-derived nutrients. The nematode provides the bacteria with protection from predators, access to nutrients, and a mechanism of dispersal. Members of the bacterial genus Photorhabdus also associate with nematodes to kill insects, and both genera of bacteria provide similar services to their different nematode hosts through unique physiological and metabolic mechanisms. We posited that these differences would be reflected in their respective genomes. To test this, we sequenced to completion the genomes of Xenorhabdus nematophila ATCC 19061 and Xenorhabdus bovienii SS-2004. As expected, both Xenorhabdus genomes encode many anti-insecticidal compounds, commensurate with their entomopathogenic lifestyle. Despite the similarities in lifestyle between Xenorhabdus and Photorhabdus bacteria, a comparative analysis of the Xenorhabdus, Photorhabdus luminescens, and P. asymbiotica genomes suggests genomic divergence. These findings indicate that evolutionary changes shaped by symbiotic interactions can follow different routes to achieve similar end points.
Interspecific competition between entomopathogenic nematodes (Steinernema) is modified by their bacterial symbionts (Xenorhabdus)  [cached]
Sicard Mathieu,Hinsinger Julie,Le Brun Nathalie,Pages Sylvie
BMC Evolutionary Biology , 2006,
Abstract: Background Symbioses between invertebrates and prokaryotes are biological systems of particular interest in order to study the evolution of mutualism. The symbioses between the entomopathogenic nematodes Steinernema and their bacterial symbiont Xenorhabdus are very tractable model systems. Previous studies demonstrated (i) a highly specialized relationship between each strain of nematodes and its naturally associated bacterial strain and (ii) that mutualism plays a role in several important life history traits of each partner such as access to insect host resources, dispersal and protection against various biotic and abiotic factors. The goal of the present study was to address the question of the impact of Xenorhabdus symbionts on the progression and outcome of interspecific competition between individuals belonging to different Steinernema species. For this, we monitored experimental interspecific competition between (i) two nematode species: S. carpocapsae and S. scapterisci and (ii) their respective symbionts: X. nematophila and X. innexi within an experimental insect-host (Galleria mellonella). Three conditions of competition between nematodes were tested: (i) infection of insects with aposymbiotic IJs (i.e. without symbiont) of both species (ii) infection of insects with aposymbiotic IJs of both species in presence of variable proportion of their two Xenorhabdus symbionts and (iii) infection of insects with symbiotic IJs (i.e. naturally associated with their symbionts) of both species. Results We found that both the progression and the outcome of interspecific competition between entomopathogenic nematodes were influenced by their bacterial symbionts. Thus, the results obtained with aposymbiotic nematodes were totally opposite to those obtained with symbiotic nematodes. Moreover, the experimental introduction of different ratios of Xenorhabdus symbionts in the insect-host during competition between Steinernema modified the proportion of each species in the adults and in the global offspring. Conclusion We showed that Xenorhabdus symbionts modified the competition between their Steinernema associates. This suggests that Xenorhabdus not only provides Steinernema with access to food sources but also furnishes new abilities to deal with biotic parameters such as competitors.
Interspecific competition between entomopathogenic nematodes (Steinernema) is modified by their bacterial symbionts (Xenorhabdus)
Mathieu Sicard, Julie Hinsinger, Nathalie Le Brun, Sylvie Pages, No?l Boemare, Catherine Moulia
BMC Evolutionary Biology , 2006, DOI: 10.1186/1471-2148-6-68
Abstract: We found that both the progression and the outcome of interspecific competition between entomopathogenic nematodes were influenced by their bacterial symbionts. Thus, the results obtained with aposymbiotic nematodes were totally opposite to those obtained with symbiotic nematodes. Moreover, the experimental introduction of different ratios of Xenorhabdus symbionts in the insect-host during competition between Steinernema modified the proportion of each species in the adults and in the global offspring.We showed that Xenorhabdus symbionts modified the competition between their Steinernema associates. This suggests that Xenorhabdus not only provides Steinernema with access to food sources but also furnishes new abilities to deal with biotic parameters such as competitors.Symbioses between the entomopathogenic nematodes Steinernema spp. and the enterobacteriacae Xenorhabdus spp. are associations in which both partners receive benefits from each other [1-3]. In the soil, the infective juveniles (IJs) of the nematodes act as vectors dispersing the bacteria from insect host to insect-host and in turn, the bacteria increase the nematode's fitness within the insects hosts [3,4]. Previous studies showed that these symbioses were highly specific and that no Steinernema spp. was able to associate with a Xenorhabdus spp. genetically distant from its natural one [2,5,6]. As the bacterial dispersion is totally dependent upon the fitness of the nematode within the insect-host, it is possible that Xenorhabdus spp. might select special traits in order to enhance their vector's fitness. It is known that Xenorhabdus spp. are beneficial to their nematodes in providing the latter with a better ability to kill the insect and feed on it [1,7,8]. Previous studies that focused on two different Steinernema species (S. carpocapsae and S. scapterisci) have provided us with insights into the association characteristics [2,5,6,9-11]. Although the two nematode species demonstrated increased fitne
Isolation and Identification of Seven Symbiotic Bacteria from Local Entomopathogenic Nematodes
七种我国昆虫病原线虫共生菌的分离与鉴定

YANG Xiu-Fen,LIU Zheng,ZHANG Ran,YANG Huai-Wen,YUAN Jing-Jing,JIAN Heng,
杨秀芬
,刘 峥,张 冉,杨怀文,袁京京,简 恒

微生物学通报 , 2008,
Abstract: The symbiotic bacterium exists in the intestines of entomopathogenic nematodes and is a potential biological agent. Systematic classification of these bacteria is scarce in China. In this paper, seven strains of symbiotic bacteria from local entomopathogenic nematodes were identified by both observation of morphology, physiological, biochemical characteristics and sequence analysis of 16S rDNA fragments.
Isolation and Identification of Seven Symbiotic Bacteria from Local Entomopathogenic Nematodes
七种我国昆虫病原线虫共生菌的分离与鉴定

YANG Xiu-Fen,LIU Zheng,ZHANG Ran,YANG Huai-Wen,YUAN Jing-Jing,JIAN Heng,
杨秀芬
,刘 峥,张 冉,杨怀文,袁京京,简 恒

微生物学报 , 2008,
Abstract: The symbiotic bacterium exists in the intestines of entomopathogenic nematodes and is a potential biological agent. Systematic classification of these bacteria is scarce in China. In this paper, seven strains of symbiotic bacteria from local entomopathogenic nematodes were identified by both observation of morphology, physiological, biochemical characteristics and sequence analysis of 16S rDNA fragments.
Variable fragment of 23S rDNA for classification and identification of Xenorhabdus
以23S rDNA一个多变区作为分子标记对致病杆菌属细菌进行分类鉴定

Zhao Jingxiu,Liu Chunlin,Qiu Lihong,Pang Yi,
Zhao J
,Liu C,Qiu L,Pang Y

微生物学报 , 2012,
Abstract: Objective]Members of Xenorhabdus are symbiotic bacteria of entomopathogenic nematodes Steinernema,and can be applied as biopesticides against insects.Therefore,a rapid and accurate method for classification and identification of Xenorhabdus is essential.Methods] An 845bp-fragment of 23S rDNA sequence of 26 strains of Xenorhabdus representing 20 described species was PCR amplified and sequenced.A phylogenetic tree of Xenorhabdus based on the sequences obtained was constructed and compared to that based on nearly complete 16S rDNA sequences for suitability as molecular maker for classification and identification of Xenorhabdus.Results] The 23S rDNA fragment contained more variable and parsimony-informative sites proportionally,and with greater pairwise distances among sequences compared to those of 16S rDNA.Conclusion] The 23S rDNA fragment can be used to identify Xenorhabdus,especially for a large number of Xenorhabdus strains obtained from field survey.
Advance of Researches on Insecticidal Toxins from Symbiotic Bacteria of Entomopathogenic Nematodes
昆虫病原线虫共生菌杀虫毒素研究进展

CUI Long,QIU Li_Hong,PANG Yi,
崔龙
,邱礼鸿,庞义

微生物学报 , 2004,
Abstract: The advanced progresses in insecticidal toxin from symbiotic bacteria of entomopathogenic nematodes were reviewed. The toxins with oral toxicities towards insects as well as relationships between oral toxicity and insecticidal toxin genes were centrally introduced. The authors' opinion in research directions in those toxins was put forward at the end of this review.
Effect of Heat Sterilization on the Bioactivity of Antibacterial Metabolites Secreted by Xenorhabdus nematophila  [PDF]
Floyd L. Inman,Leonard Holmes
Pakistan Journal of Biological Sciences , 2012,
Abstract: Photorhabdus luminescens and Xenorhabdus nematophila are entomopathogenic bacterial symbionts of beneficial nematodes Heterorhabditis bacteriophora and Steinernema carpocapsae, respectively. These bacterial symbionts are known to secrete an array of toxins, enzymes and antimicrobials that kill, bioconvert and protect the insect host for optimal nematode growth and reproduction. The present study explores heat stability of antibacterial metabolites secreted by X. nematophila. Permeate of a liquid X. nematophila culture was subjected to various sterilization treatments to observe the effects of heat sterilization on antibacterial activity. Activity was measured as bacterial sensitivity which is assayed utilizing a modified-version of the Kirby-Bauer disk diffusion method. Results demonstrate that X. nematophila produces both heat-labile and heat-stabile antibacterials that are effective against different species of bacteria. Results also indicated that heat-stabile components are more active than heat-labile components. The discovery of an environmental organism that produces both heat-stabile and heat-labile antibacterials can be exploited to manufacture these compounds for potential medical applications for human and animal use.
Identification of genes involved in the mutualistic colonization of the nematode Heterorhabditis bacteriophora by the bacterium Photorhabdus luminescens
Catherine A Easom, Susan A Joyce, David J Clarke
BMC Microbiology , 2010, DOI: 10.1186/1471-2180-10-45
Abstract: In this work we genetically tagged P. luminescens TT01 with gfp and constructed a library containing over 3200 mutants using the suicide vector, pUT-Km2. Using a combination of in vitro symbiosis assays and fluorescent microscopy we screened this library for mutants that were affected in their ability to colonize the IJ i.e. with decreased transmission frequencies. In total 8 mutants were identified with transmission frequencies of ≤ 30% compared to wild-type. These mutants were mapped to 6 different genetic loci; the pbgPE operon, galE, galU, proQ, asmA and hdfR. The pbgPE, galE and galU mutants were all predicted to be involved in LPS biosynthesis and, in support of this, we have shown that these mutants are avirulent and sensitive to the cationic antimicriobial peptide, polymyxin B. On the other hand the proQ, asmA and hdfR mutants were not affected in virulence and were either as resistant (proQ) or slightly more sensitive (asmA, hdfR) to polymyxin B than the wild-type (WT).This is the first report describing the outcome of a comprehensive screen looking for transmission mutants in Photorhabdus. In total 6 genetic loci were identified and we present evidence that all of these loci are involved in the assembly and/or maintenance of LPS and other factors associated with the cell surface. Interestingly several, but not all, of the transmission mutants identified were also avirulent suggesting that there is a significant, but not complete, genetic overlap between pathogenicity and mutualism. Therefore, this study highlights the importance of the cell surface in mediating the symbiotic and pathogenic interactions of Photorhabdus.Photorhabdus are a genus of bioluminescent, entomopathogenic bacteria that are members of the family Enterobacteriaceae and are thus closely related to Escherichia coli and other important mammalian pathogens. As part of their normal life-cycle Photorhabdus also have a mutualistic interaction with nematodes from the family Heterorhabditis (fo
Genetic and Proteomic Characterization of rpoB Mutations and Their Effect on Nematicidal Activity in Photorhabdus luminescens LN2  [PDF]
Xuehong Qiu, Xun Yan, Mingxing Liu, Richou Han
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043114
Abstract: Rifampin resistant (RifR) mutants of the insect pathogenic bacterium Photorhabdus luminescens LN2 from entomopathogenic nematode Heterorhabditis indica LN2 were genetically and proteomically characterized. The RifR mutants showed typical phase one characters of Photorhabdus bacteria, and insecticidal activity against Galleria mellonella larvae, but surprisingly influenced their nematicidal activity against axenic infective juveniles (IJs) of H. bacteriophora H06, an incompatible nematode host. 13 out of 34 RifR mutants lost their nematicidal activity against H06 IJs but supported the reproduction of H06 nematodes. 7 nematicidal-producing and 7 non-nematicidal-producing RifR mutants were respectively selected for rpoB sequence analysis. rpoB mutations were found in all 14 RifR mutants. The rpoB (P564L) mutation was found in all 7 mutants which produced nematicidal activity against H06 nematodes, but not in the mutants which supported H06 nematode production. Allelic exchange assays confirmed that the Rif-resistance and the impact on nematicidal activity of LN2 bacteria were conferred by rpoB mutation(s). The non-nematicidal-producing RifR mutant was unable to colonize in the intestines of H06 IJs, but able to colonize in the intestines of its indigenous LN2 IJs. Proteomic analysis revealed different protein expression between wild-type strain and RifR mutants, or between nematicidal-producing and non nematicidal-producing mutants. At least 7 putative proteins including DsbA, HlpA, RhlE, RplC, NamB (a protein from T3SS), and 2 hypothetical proteins (similar to unknown protein YgdH and YggE of Escherichia coli respectively) were probably involved in the nematicidal activity of LN2 bacteria against H06 nematodes. This hypothesis was further confirmed by creating insertion-deletion mutants of three selected corresponding genes (the downregulated rhlE and namB, and upregualted dsbA). These results indicate that the rpoB mutations greatly influence the symbiotic association between the symbionts and their entomopathogenic nematode hosts.
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