Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 139
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
World J Microbiol Biotechnol ; 35(7): 106, 2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-31267229

RESUMO

Xenorhabdus nematophila HB310 secreted the insecticidal protein toxin complex. Two chitinase genes, chi60 and chi70, were found in X. nematophila toxin complex locus. In order to clarify the function of two chitinases, chi60 and chi70 genes were cloned and expressed in Escherichia coli Transetta (DE3). As a result, we found that the Chi60 and Chi70 belonged to glycoside hydrolases (GH) family 18 with a molecular mass of 65 kDa and 78 kDa, respectively. When colloidal chitin was treated as the substrate, Chi60 and Chi70 were proved to have the highest enzymatic activity at pH 6.0 and 50 °C. Chi60 and Chi70 had obvious growth inhibition effect against the second larvae of Helicoverpa armigera with growth inhibiting rate of 81.99% and 90.51%. Chi70 had synergistic effect with the insecticidal toxicity of Bt Cry 1Ac, but the Chi60 had no synergistic effect with Bt Cry 1Ac. Chi60 and Chi70 showed antifungal activity against Alternaria brassicicola, Verticillium dahliae and Coniothyrium diplodiella. The results increased our understanding of the chitinases produced by X. nematophila and laid a foundation for further studies on the mechanism of the chitinases.


Assuntos
Antifúngicos/farmacologia , Quitinases/antagonistas & inibidores , Quitinases/genética , Quitinases/metabolismo , Xenorhabdus/metabolismo , Alternaria/efeitos dos fármacos , Animais , Ascomicetos/efeitos dos fármacos , Quitina/metabolismo , Quitinases/classificação , Clonagem Molecular , Sinergismo Farmacológico , Ensaios Enzimáticos , Estabilidade Enzimática , Escherichia coli/genética , Expressão Gênica , Glicosídeo Hidrolases/genética , Concentração de Íons de Hidrogênio , Inseticidas/metabolismo , Inseticidas/farmacologia , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Peso Molecular , Mariposas/efeitos dos fármacos , Mariposas/crescimento & desenvolvimento , Micotoxinas/genética , Micotoxinas/metabolismo , Filogenia , Domínios Proteicos , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Temperatura Ambiente , Verticillium/efeitos dos fármacos , Xenorhabdus/genética
2.
Nat Chem ; 11(7): 653-661, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31182822

RESUMO

Non-ribosomal peptide synthetases (NRPSs) are giant enzyme machines that activate amino acids in an assembly line fashion. As NRPSs are not restricted to the incorporation of the 20 proteinogenic amino acids, their efficient manipulation would enable microbial production of a diverse range of peptides; however, the structural requirements for reprogramming NRPSs to facilitate the production of new peptides are not clear. Here we describe a new fusion point inside the condensation domains of NRPSs that results in the development of the exchange unit condensation domain (XUC) concept, which enables the efficient production of peptides, even containing non-natural amino acids, in yields up to 280 mg l-1. This allows the generation of more specific NRPSs, reducing the number of unwanted peptide derivatives, but also the generation of peptide libraries. The XUC might therefore be suitable for the future optimization of peptide production and the identification of bioactive peptide derivatives for pharmaceutical and other applications.


Assuntos
Peptídeo Sintases/biossíntese , Engenharia de Proteínas/métodos , Aminoácidos/química , Bacillus/genética , Sequência de Bases , Escherichia coli/genética , Família Multigênica , Biblioteca de Peptídeos , Peptídeo Sintases/química , Peptídeo Sintases/genética , Photorhabdus/enzimologia , Domínios Proteicos/genética , Especificidade por Substrato , Xenorhabdus/genética
3.
Nat Chem Biol ; 15(4): 331-339, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30886436

RESUMO

Biosynthetic gene clusters (BGCs) bridging genotype and phenotype continuously evolve through gene mutations and recombinations to generate chemical diversity. Phenazine BGCs are widespread in bacteria, and the biosynthetic mechanisms of the formation of the phenazine structural core have been illuminated in the last decade. However, little is known about the complex phenazine core-modification machinery. Here, we report the diversity-oriented modifications of the phenazine core through two distinct BGCs in the entomopathogenic bacterium Xenorhabdus szentirmaii, which lives in symbiosis with nematodes. A previously unidentified aldehyde intermediate, which can be modified by multiple enzymatic and non-enzymatic reactions, is a common intermediate bridging the pathways encoded by these BGCs. Evaluation of the antibiotic activity of the resulting phenazine derivatives suggests a highly effective strategy to convert Gram-positive specific phenazines into broad-spectrum antibiotics, which might help the bacteria-nematode complex to maintain its special environmental niche.


Assuntos
Fenazinas/metabolismo , Xenorhabdus/genética , Animais , Bactérias , Proteínas de Bactérias , Família Multigênica/genética , Família Multigênica/fisiologia , Nematoides/metabolismo , Xenorhabdus/metabolismo
4.
J Ind Microbiol Biotechnol ; 46(3-4): 565-572, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30610410

RESUMO

Fabclavines, unusual peptide-polyketide-polyamine hybrids, show broad-spectrum bioactivity against a variety of different organism like Gram-positive and -negative bacteria, fungi and protozoa. We elucidated the biosynthesis of these NRPS-PKS hybrids in Xenorhabdus szentirmaii by deletion of most genes encoded in the fabclavine BGC and subsequent analysis of produced fabclavine or polyamine intermediates. Thereby, we identified shortened fabclavines similar to the bioactive zeamines. Furthermore, we analyzed the thioester reductase FclG and the free-standing condensation domain-like protein FclL in detail and observed low substrate specificity for both enzymes.


Assuntos
Proteínas de Bactérias/genética , Oligopeptídeos/biossíntese , Oxirredutases/genética , Poliaminas/química , Xenorhabdus/genética , Xenorhabdus/metabolismo , Proteínas de Bactérias/metabolismo , Vias Biossintéticas/genética , Deleção de Genes , Genes Bacterianos , Oligopeptídeos/química , Oxirredutases/metabolismo , Especificidade por Substrato
5.
Microb Biotechnol ; 12(3): 447-458, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30623566

RESUMO

CpxR is a global response regulator that negatively influences the antimicrobial activities of Xenorhabdus nematophila. Herein, the wildtype and ΔcpxR mutant of X. nematophila were cultured in a 5-l and 70-l bioreactor. The kinetic analysis showed that ΔcpxR significantly increased the cell biomass and antibiotic activity. The maximum dry cell weight (DCW) and antibiotic activity of ΔcpxR were 20.77 ± 1.56 g L-1 and 492.0 ± 31.2 U ml-1 and increased by 17.28 and 97.33% compared to the wildtype respectively. Xenocoumacin 1 (Xcn1), a major antimicrobial compound, was increased 3.07-fold, but nematophin was decreased by 48.7%. In 70-l bioreactor, DCW was increased by 18.97%, while antibiotic activity and Xcn1 were decreased by 27.71% and 11.0% compared to that in 5-l bioreactor respectively. Notably, pH had remarkable effects on the cell biomass and antibiotic activity of ΔcpxR, where ΔcpxR was sensitive to alkaline pH conditions. The optimal cell growth and antibiotic activity of ΔcpxR occurred at pH 7.0, while Xcn1 was increased 5.45- and 3.87-fold relative to that at pH 5.5 and 8.5 respectively. These findings confirmed that ΔcpxR considerably increased the biomass of X. nematophila at a late stage of fermentation. In addition, ΔcpxR significantly promoted the biosynthesis of Xcns but decreased the production of nematophin.


Assuntos
Antibacterianos/metabolismo , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Xenorhabdus/crescimento & desenvolvimento , Xenorhabdus/metabolismo , Proteínas de Bactérias/genética , Benzopiranos/metabolismo , Reatores Biológicos/microbiologia , Meios de Cultura/química , Deleção de Genes , Concentração de Íons de Hidrogênio , Indóis/metabolismo , Xenorhabdus/genética
6.
Comput Biol Chem ; 76: 293-301, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30114602

RESUMO

Here we report the first essentially complete TAome analysis for type II toxin-antitoxin (TA) system, a major class of TA modules found in bacterial system, from entomopathogenic bacterium Xenorhabdus nematophila ATCC 19061 (NCBI RefSeq NC_014228). We summarize this analysis in terms of TA locus, accession identifier, hits in conserved domain database, toxin superfamily, antitoxin superfamily and chromosomal/mobile genome/plasmid occurrences. Moreover, for TA context analyses we use six different specifications namely virulence factors, mobile genetic elements (MGE), antibiotic resistance genes, secretion systems, prophage and a classification of mobile genetic elements (ACLAME); among these hits are found for only MGE, ACLAME and prophage. A total 39 sets of TA have been discovered in which numbers of TA encoded for MGE, ACLAME and prophage are 15, 15 and 5 respectively while the remaining four have no context hit. In addition, a comparative analysis of TAome was also done with closely related bacterium Photorhabdus luminescens subsp. laumondii TTO1 (NCBI RefSeq NC_005126) and results shows that a total 8 sets of TA are conserved. Further, a bootstrap Neighbor-Joining phylogenetic tree was also constructed for major toxin protein superfamily found namely RelE, HigB, GNAT, CcdB and MazF explored in the TAome of X. nematophila. We also characterized, the most abundantly found TA module (relBE) in this TAome, functionally and transcriptionally. This first TAome analysis of type II TA modules provides new insights in multi-drug tolerance in bacterial populations.


Assuntos
Proteínas de Bactérias/genética , Toxinas Bacterianas/genética , Sistemas Toxina-Antitoxina/genética , Xenorhabdus/genética , Genômica , Photorhabdus/genética , Filogenia
7.
Arch Microbiol ; 200(2): 349-353, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29170804

RESUMO

Strain WS9, a mutualistic-associated bacterium, was isolated from an unknown entomopathogenic Steinernema nematode, collected from a litchi orchard in Friedenheim, Mpumalanga, South Africa. Based on phenotypic and phylogenetic data of the 16S rRNA, gltX, recA, dnaN, gyrB and infB gene sequences, strain WS9 is identified as X. griffiniae. Strain WS9 has antibacterial activity against Gram-positive and Gram-negative bacteria. This is the first report of an association between X. griffiniae and an unknown Steinernema species from South Africa.


Assuntos
Cromadoria/microbiologia , Simbiose/fisiologia , Xenorhabdus/fisiologia , Animais , DNA Bacteriano/genética , Fenótipo , Filogenia , RNA Ribossômico 16S/genética , África do Sul , Xenorhabdus/genética , Xenorhabdus/isolamento & purificação
8.
Arch Microbiol ; 200(4): 589-601, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29270664

RESUMO

The diversity of 43 bacterial strains isolated from Beninese entomopathogenic nematodes was investigated molecularly by analyzing the 16S rRNA, recA, and gyrB genes. Based on 16S rRNA sequence analysis, 15 bacterial strains were identified as Xenorhabdus sp., 27 strains as Photorhabdus sp., and one as Serratia sp. The Xenorhabdus strains were isolated from Steinernema nematodes and identified as Xenorhabdus indica based on 16S rRNA gene and concatenated recA and gyrB sequence analysis. However, analysis of 16S rRNA and concatenated recA and gyrB gene sequences of the Photorhabdus strains, all isolated from Heterorhabditis nematodes, resulted in two separate sub-clusters (A) and (B) within the Photorhabdus luminescens group, distinct from the existing subspecies. They share low sequence similarities with nearest phylogenetic neighbors Photorhabdus luminescens subsp. luminescens HbT, Photorhabdus luminescens subsp. caribbeanensis HG29T, and Photorhabdus luminescens subsp. noenieputensis AM7T.


Assuntos
Photorhabdus/genética , Rhabditoidea/microbiologia , Tylenchida/microbiologia , Xenorhabdus/genética , Animais , Proteínas de Bactérias/genética , Benin , DNA Bacteriano/genética , Tipagem Molecular , Filogenia , RNA Ribossômico 16S/genética , Rhabditoidea/genética , Solo/parasitologia , Simbiose , Tylenchida/genética
9.
BMC Genomics ; 18(1): 927, 2017 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-29191166

RESUMO

BACKGROUND: Xenorhabdus innexi is a bacterial symbiont of Steinernema scapterisci nematodes, which is a cricket-specialist parasite and together the nematode and bacteria infect and kill crickets. Curiously, X. innexi expresses a potent extracellular mosquitocidal toxin activity in culture supernatants. We sequenced a draft genome of X. innexi and compared it to the genomes of related pathogens to elucidate the nature of specialization. RESULTS: Using green fluorescent protein-expressing X. innexi we confirm previous reports using culture-dependent techniques that X. innexi colonizes its nematode host at low levels (~3-8 cells per nematode), relative to other Xenorhabdus-Steinernema associations. We found that compared to the well-characterized entomopathogenic nematode symbiont X. nematophila, X. innexi fails to suppress the insect phenoloxidase immune pathway and is attenuated for virulence and reproduction in the Lepidoptera Galleria mellonella and Manduca sexta, as well as the dipteran Drosophila melanogaster. To assess if, compared to other Xenorhabdus spp., X. innexi has a reduced capacity to synthesize virulence determinants, we obtained and analyzed a draft genome sequence. We found no evidence for several hallmarks of Xenorhabdus spp. toxicity, including Tc and Mcf toxins. Similar to other Xenorhabdus genomes, we found numerous loci predicted to encode non-ribosomal peptide/polyketide synthetases. Anti-SMASH predictions of these loci revealed one, related to the fcl locus that encodes fabclavines and zmn locus that encodes zeamines, as a likely candidate to encode the X. innexi mosquitocidal toxin biosynthetic machinery, which we designated Xlt. In support of this hypothesis, two mutants each with an insertion in an Xlt biosynthesis gene cluster lacked the mosquitocidal compound based on HPLC/MS analysis and neither produced toxin to the levels of the wild type parent. CONCLUSIONS: The X. innexi genome will be a valuable resource in identifying loci encoding new metabolites of interest, but also in future comparative studies of nematode-bacterial symbiosis and niche partitioning among bacterial pathogens.


Assuntos
Toxinas Bacterianas/metabolismo , Interações Hospedeiro-Patógeno , Tylenchida/microbiologia , Tylenchida/fisiologia , Xenorhabdus/patogenicidade , Aedes , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Drosophila melanogaster/efeitos dos fármacos , Drosophila melanogaster/imunologia , Drosophila melanogaster/microbiologia , Genoma Bacteriano , Proteínas de Fluorescência Verde/metabolismo , Lepidópteros/efeitos dos fármacos , Lepidópteros/imunologia , Lepidópteros/microbiologia , Masculino , Filogenia , Locos de Características Quantitativas , Simbiose , Tylenchida/efeitos dos fármacos , Tylenchida/imunologia , Virulência , Fatores de Virulência/genética , Fatores de Virulência/metabolismo , Xenorhabdus/classificação , Xenorhabdus/genética , Xenorhabdus/fisiologia
10.
Microb Cell Fact ; 16(1): 203, 2017 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29141647

RESUMO

BACKGROUND: Xenocoumacin 1 (Xcn1) and Xenocoumacin 2 (Xcn2) are the main antimicrobial compounds produced by Xenorhabdus nematophila. Culture conditions, including pH, had remarkably distinct effects on the antimicrobial activity of X. nematophila. However, the regulatory mechanism of pH on the antimicrobial activity and antibiotic production of this bacterium is still lacking. RESULTS: With the increase of initial pH, the antimicrobial activity of X. nematophila YL001 was improved. The levels of Xcn1 and nematophin at pH 8.5 were significantly (P < 0.05) higher than that at pH 5.5 and 7.0. In addition, the expression of xcnA-L, which are responsible for the production of Xcn1 was increased and the expression of xcnMN, which are required for the conversion of Xcn1 to Xcn2 was reduced at pH 8.5. Also, the expression of ompR and cpxR were decreased at pH 8.5. CONCLUSION: The alkaline pH environment was found to be beneficial for the production of Xcn1 and nematophin, which in turn led to high antimicrobial activity of X. nematophila at pH 8.5.


Assuntos
Antibacterianos/biossíntese , Benzopiranos/metabolismo , Xenorhabdus/metabolismo , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Benzopiranos/farmacologia , Meios de Cultura/química , Fermentação , Concentração de Íons de Hidrogênio , Indóis/metabolismo , Indóis/farmacologia , Xenorhabdus/genética
11.
Nat Microbiol ; 2(12): 1676-1685, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28993611

RESUMO

Xenorhabdus and Photorhabdus species dedicate a large amount of resources to the production of specialized metabolites derived from non-ribosomal peptide synthetase (NRPS) or polyketide synthase (PKS). Both bacteria undergo symbiosis with nematodes, which is followed by an insect pathogenic phase. So far, the molecular basis of this tripartite relationship and the exact roles that individual metabolites and metabolic pathways play have not been well understood. To close this gap, we have significantly expanded the database for comparative genomics studies in these bacteria. Clustering the genes encoded in the individual genomes into hierarchical orthologous groups reveals a high-resolution picture of functional evolution in this clade. It identifies groups of genes-many of which are involved in secondary metabolite production-that may account for the niche specificity of these bacteria. Photorhabdus and Xenorhabdus appear very similar at the DNA sequence level, which indicates their close evolutionary relationship. Yet, high-resolution mass spectrometry analyses reveal a huge chemical diversity in the two taxa. Molecular network reconstruction identified a large number of previously unidentified metabolite classes, including the xefoampeptides and tilivalline. Here, we apply genomic and metabolomic methods in a complementary manner to identify and elucidate additional classes of natural products. We also highlight the ability to rapidly and simultaneously identify potentially interesting bioactive products from NRPSs and PKSs, thereby augmenting the contribution of molecular biology techniques to the acceleration of natural product discovery.


Assuntos
Produtos Biológicos , Nematoides/microbiologia , Photorhabdus/metabolismo , Simbiose , Xenorhabdus/metabolismo , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , DNA Bacteriano/isolamento & purificação , Genoma Bacteriano/genética , Interações Hospedeiro-Patógeno/genética , Interações Hospedeiro-Patógeno/fisiologia , Redes e Vias Metabólicas , Metaboloma , Nematoides/fisiologia , Peptídeo Sintases/metabolismo , Photorhabdus/classificação , Photorhabdus/genética , Policetídeo Sintases/metabolismo , Metabolismo Secundário , Xenorhabdus/classificação , Xenorhabdus/genética
12.
Parasit Vectors ; 10(1): 440, 2017 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-28934970

RESUMO

BACKGROUND: Aedes aegypti is a potential vector of West Nile, Japanese encephalitis, chikungunya, dengue and Zika viruses. Alternative control measurements of the vector are needed to overcome the problems of environmental contamination and chemical resistance. Xenorhabdus and Photorhabdus are symbionts in the intestine of entomopathogenic nematodes (EPNs) Steinernema spp. and Heterorhabditis spp. These bacteria are able to produce a broad range of bioactive compounds including antimicrobial, antiparasitic, cytotoxic and insecticidal compounds. The objectives of this study were to identify Xenorhabdus and Photorhabdus isolated from EPNs in upper northern Thailand and to study their larvicidal activity against Ae. aegypti larvae. RESULTS: A total of 60 isolates of symbiotic bacteria isolated from EPNs consisted of Xenorhabdus (32 isolates) and Photorhabdus (28 isolates). Based on recA gene sequencing, BLASTN and phylogenetic analysis, 27 isolates of Xenorhabdus were identical and closely related to X. stockiae, 4 isolates were identical to X. miraniensis, and one isolate was identical to X. ehlersii. Twenty-seven isolates of Photorhabdus were closely related to P. luminescens akhurstii and P. luminescens hainanensis, and only one isolate was identical and closely related to P. luminescens laumondii. Xenorhabdus and Photorhabdus were lethal to Ae aegypti larvae. Xenorhabdus ehlersii bMH9.2_TH showed 100% efficiency for killing larvae of both fed and unfed conditions, the highest for control of Ae. aegypti larvae and X. stockiae (bLPA18.4_TH) was likely to be effective in killing Ae. aegypti larvae given the mortality rates above 60% at 72 h and 96 h. CONCLUSIONS: The common species in the study area are X. stockiae, P. luminescens akhurstii, and P. luminescens hainanensis. Three symbiotic associations identified included P. luminescens akhurstii-H. gerrardi, P. luminescens hainanensis-H. gerrardi and X. ehlersii-S. Scarabaei which are new observations of importance to our knowledge of the biodiversity of, and relationships between, EPNs and their symbiotic bacteria. Based on the biological assay, X. ehlersii bMH9.2_TH begins to kill Ae. aegypti larvae within 48 h and has the most potential as a pathogen to the larvae. These data indicate that X. ehlersii may be an alternative biological control agent for Ae. aegypti and other mosquitoes.


Assuntos
Aedes/microbiologia , Antibiose , Photorhabdus/isolamento & purificação , Photorhabdus/fisiologia , Rhabditoidea/microbiologia , Tylenchida/microbiologia , Xenorhabdus/isolamento & purificação , Xenorhabdus/fisiologia , Animais , Feminino , Larva/microbiologia , Masculino , Photorhabdus/classificação , Photorhabdus/genética , Filogenia , Rhabditoidea/fisiologia , Simbiose , Tailândia , Tylenchida/fisiologia , Xenorhabdus/classificação , Xenorhabdus/genética
13.
J Insect Physiol ; 101: 82-90, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28716396

RESUMO

Xenorhabdus nematophila is a symbiotic bacterium of the entomopathogenic nematode Steinernema carpocapsae (Weiser). It produces several toxic proteins which interfere with the immune system of insects. The current study shows that purified pilin protein could be a virulence trait of X. nematophila. The fifth instar larvae of Spodoptera exigua (Hübner) was injected with purified pilin. Changes in the cellular defenses in terms of total haemocyte counts and granulocyte percentage and humoral factors including total protease, phospholipase A2, and phenoloxidase activities (humoral defense) as well as the expression of the three main antimicrobial peptides attacin, cecropin, and spodoptericin were measured at specific times. The level of THC and granulocytes in larvae with different concentrations of pilin protein were less than the negative control. Also agglutination of haemocytes was observed 8-16h post-injection. The pilin protein activated phenoloxidase in the initial hour post-injection, by 2hpi, activity was stable. The activities of phospholipase A2 and protease activities reached maximum levels at 12 and 4hpi, respectively, and then decreased. The expressions of attacin, cecropin, and spodoptericin in larvae treated with pilin protein were up-regulated above that of the normal sample. The overexpression of cecropin was greater than the other antimicrobial protein mRNA transcripts. The spodoptericin expression had an irregular trend while expressions of attacin and cecropin reached maximum levels at 4hpi and then decreased. Generally, after the injection of pilin protein, the cellular and humoral immune system of S. exigua is activated but this toxin was able to inhibit them. This is the first report of the role of pilin protein when the bacterial symbiont of S. carpocapsae encounters the humoral defense of an insect.


Assuntos
Peptídeos Catiônicos Antimicrobianos/genética , Proteínas de Fímbrias/genética , Imunidade Inata , Spodoptera/imunologia , Spodoptera/microbiologia , Xenorhabdus/fisiologia , Animais , Peptídeos Catiônicos Antimicrobianos/metabolismo , Proteínas de Fímbrias/metabolismo , Larva/crescimento & desenvolvimento , Larva/imunologia , Larva/microbiologia , Análise de Sequência de DNA , Spodoptera/crescimento & desenvolvimento , Xenorhabdus/genética
14.
Environ Microbiol ; 19(10): 4080-4090, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28654175

RESUMO

Effective iron acquisition and fine-tuned intracellular iron storage systems are the main prerequisites for a successful host invasion by a pathogen. Bacteria have developed several different strategies to sequester this essential element from their environment, one relies on the secretion of low molecular weight compounds with high affinity for ferric iron, the so-called siderophores. Here, we report hydroxamate siderophore structures produced by entomopathogenic bacteria of the species Xenorhabdus and Photorhabdus, which are known for their potential to produce bioactive natural products, required for their role as nematode symbiont and insect pathogen. Four siderophores could be identified, namely aerobactin, putrebactin, avaroferrin and ochrobactin C, which was found previously only in marine bacteria. While the putrebactin and avaroferrin producing biosynthesis gene cluster (BGC) is more widespread and most likely was present in a common ancestor of these bacteria, the aerobactin and ochrobactin producing BGC was probably taken up by a few strains individually. For aerobactin a role in virulence towards Galleria mellonella larvae is shown.


Assuntos
Ácidos Hidroxâmicos/química , Peptídeos Cíclicos/química , Photorhabdus/metabolismo , Putrescina/análogos & derivados , Sideróforos/química , Succinatos/química , Xenorhabdus/metabolismo , Animais , Ácidos Hidroxâmicos/análise , Ferro/metabolismo , Mariposas/efeitos dos fármacos , Peptídeos Cíclicos/análise , Photorhabdus/genética , Photorhabdus/patogenicidade , Putrescina/análise , Putrescina/química , Succinatos/análise , Virulência , Fatores de Virulência , Xenorhabdus/genética , Xenorhabdus/patogenicidade
15.
Curr Microbiol ; 74(8): 938-942, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28526895

RESUMO

Xenorhabdus species are normally closely associated with entomopathogenic nematodes of the family Steinernematidae. Strain F2, isolated from Steinernema nguyeni, was identified as Xenorhabdus bovienii and strains J194 and SB10, isolated from Steinernema jeffreyense and Steinernema sacchari as Xenorhabdus khoisanae, based on phenotypic characteristics and sequencing of 16S rRNA and housekeeping genes dnaN, gltX, gyrB, infB and recA. All three strains produced antimicrobial compounds that inhibited the growth of Gram-positive and Gram-negative bacteria. This is the first report of associations between strains of the symbiotic bacteria X. bovienii with S. nguyeni, and X. khoisanae with S. jeffreyense and S. sacchari. This provides evidence that strains of Xenorhabdus spp. may switch between nematode species within the same clade and between different clades.


Assuntos
Simbiose , Tylenchida/microbiologia , Xenorhabdus/classificação , Xenorhabdus/isolamento & purificação , Animais , Anti-Infecciosos/metabolismo , Proteínas de Bactérias/genética , Técnicas de Tipagem Bacteriana , Análise por Conglomerados , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Xenorhabdus/genética , Xenorhabdus/fisiologia
16.
J Bacteriol ; 199(15)2017 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-28484049

RESUMO

In mutually beneficial and pathogenic symbiotic associations, microbes must adapt to the host environment for optimal fitness. Both within an individual host and during transmission between hosts, microbes are exposed to temporal and spatial variation in environmental conditions. The phenomenon of phenotypic variation, in which different subpopulations of cells express distinctive and potentially adaptive characteristics, can contribute to microbial adaptation to a lifestyle that includes rapidly changing environments. The environments experienced by a symbiotic microbe during its life history can be erratic or predictable, and each can impact the evolution of adaptive responses. In particular, the predictability of a rhythmic or cyclical series of environments may promote the evolution of signal transduction cascades that allow preadaptive responses to environments that are likely to be encountered in the future, a phenomenon known as adaptive prediction. In this review, we summarize environmental variations known to occur in some well-studied models of symbiosis and how these may contribute to the evolution of microbial population heterogeneity and anticipatory behavior. We provide details about the symbiosis between Xenorhabdus bacteria and Steinernema nematodes as a model to investigate the concept of environmental adaptation and adaptive prediction in a microbial symbiosis.


Assuntos
Adaptação Biológica , Rabditídios/microbiologia , Simbiose , Xenorhabdus/genética , Xenorhabdus/fisiologia , Adaptação Fisiológica , Animais
17.
BMC Evol Biol ; 17(1): 100, 2017 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-28412935

RESUMO

BACKGROUND: Steinernematid nematodes form obligate symbioses with bacteria from the genus Xenorhabdus. Together Steinernema nematodes and their bacterial symbionts successfully infect, kill, utilize, and exit their insect hosts. During this process the nematodes and bacteria disassociate requiring them to re-associate before emerging from the host. This interaction can be complicated when two different nematodes co-infect an insect host. RESULTS: Non-cognate nematode-bacteria pairings result in reductions for multiple measures of success, including total progeny production and virulence. Additionally, nematode infective juveniles carry fewer bacterial cells when colonized by a non-cognate symbiont. Finally, we show that Steinernema nematodes can distinguish heterospecific and some conspecific non-cognate symbionts in behavioral choice assays. CONCLUSIONS: Steinernema-Xenorhabdus symbioses are tightly governed by partner recognition and fidelity. Association with non-cognates resulted in decreased fitness, virulence, and bacterial carriage of the nematode-bacterial pairings. Entomopathogenic nematodes and their bacterial symbionts are a useful, tractable, and reliable model for testing hypotheses regarding the evolution, maintenance, persistence, and fate of mutualisms.


Assuntos
Evolução Biológica , Aptidão Genética , Rabditídios/fisiologia , Simbiose , Xenorhabdus/fisiologia , Animais , Insetos/parasitologia , Filogenia , Rabditídios/classificação , Rabditídios/genética , Rabditídios/patogenicidade , Virulência , Xenorhabdus/classificação , Xenorhabdus/genética
18.
Microbiology ; 163(4): 510-522, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28430102

RESUMO

Xenorhabdus bovienii bacteria have a dual lifestyle: they are mutualistic symbionts to many species of Steinernema nematodes and are pathogens to a wide array of insects. Previous studies have shown that virulence of X.bovienii-Steinernema spp. pairs decreases when the nematodes associate with non-cognate bacterial strains. However, the virulence of the X. bovienii strains alone has not been fully investigated. In this study, we characterized the virulence of nine X. bovienii strains in Galleria mellonella and Spodoptera littoralis and performed a comparative genomic analysis to correlate observed phenotypes with strain genotypes. Two X. bovienii strains were found to be highly virulent against the tested insect hosts, while three strains displayed attenuated insect virulence. Comparative genomic analyses revealed the presence of several clusters present only in virulent strains, including a predicted type VI secretion system (T6SS). We performed intra-species-competition assays, and showed that the virulent T6SS+ strains generally outcompeted the less virulent T6SS- strains. Thus, we speculate that the T6SS in X. bovienii may be another addition to the arsenal of antibacterial mechanisms expressed by these bacteria in an insect, where it could potentially play three key roles: (1) competition against the insect host microbiota; (2) protection of the insect cadaver from necrotrophic microbial competitors; and (3) outcompeting other Xenorhabdus species and/or strains when co-infections occur.


Assuntos
Spodoptera/microbiologia , Sistemas de Secreção Tipo VI/genética , Xenorhabdus/genética , Xenorhabdus/patogenicidade , Animais , Hibridização Genômica Comparativa , Genoma Bacteriano/genética , Nematoides/microbiologia , Filogenia , Virulência/genética
19.
Appl Environ Microbiol ; 83(12)2017 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-28389546

RESUMO

Xenorhabdus nematophila bacteria are mutualistic symbionts of Steinernema carpocapsae nematodes and pathogens of insects. The X. nematophila global regulator Lrp controls the expression of many genes involved in both mutualism and pathogenic activities, suggesting a role in the transition between the two host organisms. We previously reported that natural populations of X. nematophila exhibit various levels of Lrp expression and that cells expressing relatively low levels of Lrp are optimized for virulence in the insect Manduca sexta The adaptive advantage of the high-Lrp-expressing state was not established. Here we used strains engineered to express constitutively high or low levels of Lrp to test the model in which high-Lrp-expressing cells are adapted for mutualistic activities with the nematode host. We demonstrate that high-Lrp cells form more robust biofilms in laboratory media than do low-Lrp cells, which may reflect adherence to host tissues. Also, our data showed that nematodes cultivated with high-Lrp strains are more frequently colonized than are those associated with low-Lrp strains. Taken together, these data support the idea that high-Lrp cells have an advantage in tissue adherence and colonization initiation. Furthermore, our data show that high-Lrp-expressing strains better support nematode reproduction than do their low-Lrp counterparts under both in vitro and in vivo conditions. Our data indicate that heterogeneity of Lrp expression in X. nematophila populations provides diverse cell populations adapted to both pathogenic (low-Lrp) and mutualistic (high-Lrp) states.IMPORTANCE Host-associated bacteria experience fluctuating conditions during both residence within an individual host and transmission between hosts. For bacteria that engage in evolutionarily stable, long-term relationships with particular hosts, these fluctuations provide selective pressure for the emergence of adaptive regulatory mechanisms. Here we present evidence that the bacterium Xenorhabdus nematophila uses various levels of the transcription factor Lrp to optimize its association with its two animal hosts, nematodes and insects, with which it behaves as a mutualist and a pathogen, respectively. Building on our previous finding that relatively low cellular levels of Lrp are optimal for pathogenesis, we demonstrate that, conversely, high levels of Lrp promote mutualistic activities with the Steinernema carpocapsae nematode host. These data suggest that X. nematophila has evolved to utilize phenotypic variation between high- and low-Lrp-expression states to optimize its alternating behaviors as a mutualist and a pathogen.


Assuntos
Proteínas de Bactérias/metabolismo , Rabditídios/microbiologia , Rabditídios/fisiologia , Simbiose , Fatores de Transcrição/metabolismo , Xenorhabdus/fisiologia , Animais , Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica , Fatores de Transcrição/genética , Virulência , Xenorhabdus/genética , Xenorhabdus/crescimento & desenvolvimento , Xenorhabdus/patogenicidade
20.
J Invertebr Pathol ; 148: 43-50, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28438456

RESUMO

PirAB (Photorhabdus insect-related proteins, PirAB) toxin was initially found in the Photorhabdus luminescens TT01 strain and has been shown to be a binary toxin with high insecticidal activity. Based on GenBank data, this gene was also found in the Xenorhabdus nematophila genome sequence. The predicted amino acid sequence of pirA and pirB in the genome of X. nematophila showed 51% and 50% identity with those gene sequences from P. luminescens. The purpose of this experiment is to identify the relevant information for this toxin gene in X. nematophila. The pirA, pirB and pirAB genes of X. nematophila HB310 were cloned and expressed in Escherichia coli BL21 (DE3) using the pET-28a vector. A PirAB-fusion protein (PirAB-F) was constructed by linking the pirA and pirB genes with the flexible linker (Gly)4 DNA encoding sequence and then efficiently expressed in E. coli. The hemocoel and oral insecticidal activities of the recombinant proteins were analyzed against the larvae of Galleria mellonella. The results show that PirA/B alone, PirA/B mixture, co-expressed PirAB protein, and PirAB-F all had no oral insecticidal activity against the second-instar larvae of G. mellonella. Only PirA/B mixture and co-expressed PirAB protein had hemocoel insecticidal activity against G. mellonella fifth-instar larvae, with an LD50 of 2.718µg/larva or 1.566µg/larva, respectively. Therefore, we confirmed that PirAB protein of X. nematophila HB310 is a binary insecticidal toxin. The successful expression and purification of PirAB laid a foundation for further studies on the function, insecticidal mechanism and expression regulation of the binary toxin.


Assuntos
Proteínas de Bactérias/farmacologia , Inseticidas/farmacologia , Lepidópteros/efeitos dos fármacos , Controle Biológico de Vetores/métodos , Xenorhabdus/química , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Inseticidas/química , Xenorhabdus/genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA