RESUMO
Gram-negative bacteria of the genus Xenorhabdus exhibit a mutualistic association with steinernematid entomopathogenic nematodes and a pathogenic relationship with insects. Here we describe two isolates of the entomopathogenic nematode Steinernema aciari collected from China and Japan. 16S rRNA gene sequence similarity and phylogenetic analysis indicated that the isolates obtained from S. aciari belonged to the genus Xenorhabdus. Multilocus sequence analysis based on five universal protein-coding gene sequences revealed that the isolates were closely related to Xenorhabdus ehlersii DSM 16337(T) and Xenorhabdus griffiniae ID10(T) but that they exhibited <97â% sequence similarity with these reference strains, which indicated that the isolates were distinct from previously described species. Based on these genetic differences and several differential phenotypic traits, we propose that the isolates represent a novel species of the genus Xenorhabdus, for which we propose the name Xenorhabdus ishibashii sp. nov. The type strain is GDh7(T) (â=âDSM 22670(T) â=âCGMCC 1.9166(T)).
Assuntos
Filogenia , Rabditídios/microbiologia , Xenorhabdus/classificação , Animais , Técnicas de Tipagem Bacteriana , China , DNA Bacteriano/genética , Genes Bacterianos , Japão , Dados de Sequência Molecular , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Xenorhabdus/genética , Xenorhabdus/isolamento & purificaçãoRESUMO
Photorhabdus luminescens subsp. akhurstii LN2 from Heterorhabditis indica LN2 showed nematicidal activity against axenic Heterorhabditis bacteriophora H06 infective juveniles (IJs). Transposon mutagenesis identified an LN2 mutant that supports the growth of H06 nematodes. Tn5 disrupted the namA gene, encoding a novel 364-residue protein and involving the nematicidal activity. The green fluorescent protein-labeled namA mutant was unable to colonize the intestines of H06 IJs.
Assuntos
Antinematódeos/toxicidade , Proteínas de Bactérias/genética , Photorhabdus/genética , Rhabditoidea/efeitos dos fármacos , Fatores de Virulência/genética , Sequência de Aminoácidos , Animais , Proteínas de Bactérias/toxicidade , Sequência de Bases , Elementos de DNA Transponíveis , DNA Bacteriano/química , DNA Bacteriano/genética , Técnicas de Inativação de Genes , Ordem dos Genes , Dados de Sequência Molecular , Mutagênese Insercional , Photorhabdus/patogenicidade , Análise de Sequência de DNA , Fatores de Virulência/toxicidadeRESUMO
Gram-negative bacteria, Photorhabdus luminescens and P. temperata, form a mutualistic association with entomopathogenic heterorhabditid nematodes while P. asymbiotica is known as an opportunistic human pathogen that causes disseminated bacteremic spread on two continents, the United States and Australia. In the course of our phylogenetic study of Photorhabdus bacteria associated with Japanese Heterorhabditis nematodes, we found two Photorhabdus isolates (Photorhabdus sp. Cbkj163 and OnIr40) whose partial 16S rRNA gene sequence showed high similarities to clinical isolates of this pathogen from Heterorhabditis indica. The phylogenetic study, based upon the gyrase subunit B gene sequences of the two isolates, revealed clustering with these clinical isolates of P. asymbiotica from both the United States and Australia but not with other Photorhabdus bacteria associated with nematodes. The two bacterial isolates were also found to share microbiological and biochemical characteristics with clinical and entomopathogenic Photorhabdus strains. Moreover, not only the two novel Photorhabdus isolates but also an Australian clinical isolate of P. asymbiotica formed mutualistic association with H. indica isolates. These data suggest that the bacteria isolated from H. indica CbKj163 and OnIr40 are a novel subspecies of P. asymbiotica, and that some clinical isolates of P. asymbiotica could have originated from bacteria associated with entomopathogenic nematodes.