A novel species of Xenorhabdus, family Enterobacteriaceae: Xenorhabdus indica sp. nov., symbiotically associated with entomopathogenic nematode Steinernema thermophilum Ganguly and Singh, 2000. (original) (raw)
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FEMS Microbiology Ecology, 2000
Xenorhabdus symbionts were isolated from infective juveniles of Steinernema cubanum, an entomopathogenic nematode isolated in western Cuba. A polyphasic approach, including phenotypic tests, restriction polymorphism analysis of PCRamplified 16S rRNA genes and DNA-DNA hybridizations with determination of the vT m , was used to characterize this Xenorhabdus isolate. All methods converged to the conclusion that the isolate was a strain of Xenorhabdus poinarii. Until today, this species was only isolated from Steinernema glaseri and was considered to be specific to this nematode species. From the closely phylogenetic relatedness of S. cubanum and S. glaseri, which is supported by morphological and genotypic similarities, one can assume that the divergence of these two species is relatively recent. The speciation of the respective symbiotic bacteria may be in course, but at the present time, phenotypic and genotypic divergence is not sufficient to delineate two Xenorhabdus species.
Xenorhabdus ishibashii sp. nov., isolated from the entomopathogenic nematode Steinernema aciari
INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2012
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 16337T and Xenorhabdus griffiniae ID10T but that they exhibited <97 % 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 Xenorh...
International Journal of Systematic Bacteriology, 1993
The levels of DNA relatedness for a broad sample ofXenorhabdus strains isolated from different species of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) and from different geographical sources were estimated by the hydroxyapatite method. The level of DNA-DNA relatedness for the two phases of each isolate tested was not significantly different from lo%, demonstrating unequivocally that the phase variation demonstrated by all Xenorhabdus spp. is not due to contamination. The isolates of the described Xenorhabdus species coalesced into different DNA relatedness groups, confirming that Xenorhubdus nemutophilus, Xenorhabdus bovienii, Xenorhubdus poinarii, and Xenorhabdus beddingii, defined on the basis of phenotypic differences, are valid species. The symbiont of Steinernemu intermedia also coalesced with the X. bovienii isolates. This was the only symbiont of seven recently described and unamed Steinernema spp. (including Steinernemu ritteri, Steinemem rara, and Steinernemu anomali) that formed a group with any of the previously described Xenorhabdus species; new species descriptions are required to accommodate the other taxa, but too few isolates were available to allow satisfactory descriptions of them. The DNA relatedness data also showed that the bacteria currently classified as Xenorhabdus luminescens are significantly different from all other Xenorhubdus strains. These data strongly support indications from previous studies of phenotypic characteristics, cellular fatty acids, and DNA relatedness that X. luminescens should be classified as a separate genus, A new genus, Photorhabdus, with an amended description of the type species, Photorhabdus luminescens, is proposed.
Current Microbiology, 2017
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.
Journal of helminthology, 2014
The entomopathogenic nematode Steinernema yirgalemense is considered a promising agent in the biocontrol of insects. However, little is known about the bacteria living in symbiosis with the nematode. In this study, we have identified the only available bacterial strain (157-C) isolated from S. yirgalemense, as a member of the species Xenorhabdus indica. Identification was based on 16S rDNA, recA, dnaN, gltX, gyrB and infB gene sequence analyses. The relatedness of strain 157-C to the type strain of X. indica (DSM 17 382) was confirmed with DNA-DNA hybridization. The phenotypic characteristics of strain 157-C are similar to those described for the type strain of X. indica. This is the first report associating X. indica with S. yirgalemense.
INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2013
Bacterial strain SF87T, and additional strains SF80, SF362 and 106-C, isolated from the nematode Steinernema khoisanae, are non-bioluminescent Gram-reaction-negative bacteria that share many of the carbohydrate fermentation reactions recorded for the type strains of recognized Xenorhabdus species. Based on 16S rRNA gene sequence data, strain SF87T is shown to be closely related (98 % similarity) to Xenorhabdus hominickii DSM 17903T. Nucleotide sequences of strain SF87 obtained from the recA, dnaN, gltX, gyrB and infB genes showed 96–97 % similarity with Xenorhabdus miraniensis DSM 17902T . However, strain SF87 shares only 52.7 % DNA–DNA relatedness with the type strain of X. miraniensis , confirming that it belongs to a different species. Strains SF87T, SF80, SF362 and 106-C are phenotypically similar to X. miraniensis and X. beddingii , except that they do not produce acid from aesculin. These strains are thus considered to represent a novel species of the genus Xenorhabdus , for w...
Systematic and Applied Microbiology, 1992
As part of an effort to elucidate the molecular basis of phase variation in Xenorhabdus, the two phases of X. nematophilus were examined for evidence of genomic rearrangements. No DNA sequence rearrangement was detected by RFLP analysis or Southern Cross hybridization of total DNA. Differential digestion efficiency by various restriction enzymes strongly indicated that the DNA of each of the Xenorhabdus species is highly methylated at both adenine and cytosine residues. The differential response to SmaI digestion by European and American isolates of X. nematophilus suggests a geographic variation in this species.
Journal of Invertebrate Pathology, 2010
Xenorhabdus spp., are gram-negative bacterial symbionts of entomopathogenic nematodes in the genus Steinernema. A specialized and intimate relationship exists between nematode and bacteria, affecting many of their life history traits, such as nutrition, dispersal, host-finding, foraging and defense from biotic and abiotic factors. Xenorhabdus currently comprises more than 20 species isolated from Steinernema spp. with diverse host range, host foraging behavior, reproductive modes and environmental tolerance. Xenorhabdus phylogenies have historically been based on 16s rDNA sequence analyses, and only recently has data from housekeeping genes been employed. The prevalence of lateral gene transfer among bacteria calls for a wider perspective when considering their phylogeny. With the increasing number of Xenorhabdus species and strains, various perspectives need to be considered for investigating the evolutionary history of these nematode bacterial symbionts, In this study, we reconstruct the evolutionary histories of 30 species of Xenorhabdus considering the traditional 16s rDNA gene region as well as the housekeeping genes recA and serC. Datasets were analyzed individually and then combined, using a variety of phylogenetic criteria.