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Steinernema poinari (Nematoda: Steinernematidae): a new symbiotic host of entomopathogenic bacteria Xenorhabdus bovienii.

ABSTRACT: Three strains of symbiotic bacteria were isolated from an entomopathogenic nematode Steinernema poinari retrieved from soil in eastern Poland. Using 16S rDNA, recA, gltX, gyrB, and dnaN gene sequences for phylogenetic analysis, these strains were shown to belong to the species Xenorhabdus bovienii. The nucleotide identity between the studied S. poinari microsymbionts and other X. bovienii strains calculated for 16S rDNA and concatenated sequences of four protein-coding genes was 98.7-100% and 97.9-99.5%, respectively. The phenotypic properties of the isolates also supported their close phylogenetic relationship with X. bovienii. All three tested X. bovienii strains of different Steinernema clade origin supported the recovery of infective juveniles and subsequent development of the nematode population. However, the colonization degree of new infective juvenile generations was significantly affected by the bacterial host donor/recipient. The colonization degree of infective juveniles reared on bacterial symbionts deriving from a non-cognate clade of nematodes was extremely low, but proved the possible host-switching between non-related Steinernema species.

SUBMITTER: Sajnaga E

PROVIDER: S-EPMC6182613 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Steinernema poinari (Nematoda: Steinernematidae): a new symbiotic host of entomopathogenic bacteria Xenorhabdus bovienii.

Sajnaga Ewa E Kazimierczak Waldemar W Skowronek Marcin M Lis Magdalena M Skrzypek Tomasz T Waśko Adam A

Archives of microbiology 20180626 9

Three strains of symbiotic bacteria were isolated from an entomopathogenic nematode Steinernema poinari retrieved from soil in eastern Poland. Using 16S rDNA, recA, gltX, gyrB, and dnaN gene sequences for phylogenetic analysis, these strains were shown to belong to the species Xenorhabdus bovienii. The nucleotide identity between the studied S. poinari microsymbionts and other X. bovienii strains calculated for 16S rDNA and concatenated sequences of four protein-coding genes was 98.7-100% and 97 ...[more]

PMID: 29946739

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Project description:UNLABELLED:Microbial symbionts provide benefits that contribute to the ecology and fitness of host plants and animals. Therefore, the evolutionary success of plants and animals fundamentally depends on long-term maintenance of beneficial associations. Most work investigating coevolution and symbiotic maintenance has focused on species-level associations, and studies are lacking that assess the impact of bacterial strain diversity on symbiotic associations within a coevolutionary framework. Here, we demonstrate that fitness in mutualism varies depending on bacterial strain identity, and this is consistent with variation shaping phylogenetic patterns and maintenance through fitness benefits. Through genome sequencing of nine bacterial symbiont strains and cophylogenetic analysis, we demonstrate diversity among Xenorhabdus bovienii bacteria. Further, we identified cocladogenesis between Steinernema feltiae nematode hosts and their corresponding X. bovienii symbiont strains, indicating potential specificity within the association. To test the specificity, we performed laboratory crosses of nematode hosts with native and nonnative symbiont strains, which revealed that combinations with the native bacterial symbiont and closely related strains performed significantly better than those with more divergent symbionts. Through genomic analyses we also defined potential factors contributing to specificity between nematode hosts and bacterial symbionts. These results suggest that strain-level diversity (e.g., subspecies-level differences) in microbial symbionts can drive variation in the success of host-microbe associations, and this suggests that these differences in symbiotic success could contribute to maintenance of the symbiosis over an evolutionary time scale. IMPORTANCE:Beneficial symbioses between microbes and plant or animal hosts are ubiquitous, and in these associations, microbial symbionts provide key benefits to their hosts. As such, host success is fundamentally dependent on long-term maintenance of beneficial associations. Prolonged association between partners in evolutionary time is expected to result in interactions in which only specific partners can fully support symbiosis. The contribution of bacterial strain diversity on specificity and coevolution in a beneficial symbiosis remains unclear. In this study, we demonstrate that strain-level differences in fitness benefits occur in beneficial host-microbe interactions, and this variation likely shapes phylogenetic patterns and symbiotic maintenance. This highlights that symbiont contributions to host biology can vary significantly based on very-fine-scale differences among members of a microbial species. Further, this work emphasizes the need for greater phylogenetic resolution when considering the causes and consequences of host-microbe interactions.

Project description:Three bacterial strains, XENO-2T, XENO-7T, and XENO-10T, isolated from Steinernema entomopathogenic nematodes, were found to represent novel Xenorhabdus species. In this study, we describe these new species by whole-genome and whole-proteome phylogenomic reconstructions, by calculating sequence identity scores using core genome sequences, and by phenotypic characterization. Phylogenomic reconstructions using ribosomal and house-keeping genes, and whole-genome and whole-proteome sequences show that XENO-2T and XENO-10T are closely related to Xenorhabdus japonica DSM 16522T and that XENO-7T is closely related to Xenorhabdus bovienii subsp. africana XENO-1T and to X. bovienii subsp. bovienii T228T. The dDDH values between XENO-2T and XENO-10T and between XENO-2T and X. japonica DSM 16522T are 56.4 and 51.8%, respectively. The dDDH value between XENO-10T and X. japonica DSM 16522T is 53.4%. The dDDH values between XENO-7T and X. bovienii subsp. africana XENO-1T and between XENO-7T and X. bovienii subsp. bovienii T228T are 63.6 and 69.4%, respectively. These dDDH values are below the 70% divergence threshold for prokaryotic species delineation. The newly described species are highly pathogenic to G. mellonella larvae, grow at pH between 5 and 9 (optimum 5-7), at salt concentrations of 1-3% (optimum 1-2%), and temperatures between 20 and 37 °C (optimum 28-30 °C). Biochemical tests such as lysine decarboxylase, ornithine decarboxylase, urease, gelatinase, citrate utilization, indole and acetoin production, and cytochrome oxidase tests allow to differentiate the novel species from their more closely related species. Considering these genetic and phenotypic divergencies, we propose the following new species: Xenorhabdus aichiensis sp. nov. with XENO-7T (= CCM 9233T = CCOS 2024T) as the type strain, Xenorhabdus anantnagensis sp. nov., with XENO-2T (= CCM 9237T = CCOS 2023T) as the type strain, and Xenorhabdus yunnanensis sp. nov., with XENO-10T (= CCM 9322T = CCOS 2071T) as the type strain. Our study contributes to a better understanding of the biodiversity and phylogenetic relationships of entomopathogenic bacteria associated with insect parasitic nematodes.

Project description:BackgroundXenorhabdus bacteria engage in a beneficial symbiosis with Steinernema nematodes, in part by providing activities that help kill and degrade insect hosts for nutrition. Xenorhabdus strains (members of a single species) can display wide variation in host-interaction phenotypes and genetic potential indicating that strains may differ in their encoded symbiosis factors, including secreted metabolites.MethodsTo discern strain-level variation among symbiosis factors, and facilitate the identification of novel compounds, we performed a comparative analysis of the genomes of 10 Xenorhabdus bovienii bacterial strains.ResultsThe analyzed X. bovienii draft genomes are broadly similar in structure (e.g. size, GC content, number of coding sequences). Genome content analysis revealed that general classes of putative host-microbe interaction functions, such as secretion systems and toxin classes, were identified in all bacterial strains. In contrast, we observed diversity of individual genes within families (e.g. non-ribosomal peptide synthetase clusters and insecticidal toxin components), indicating the specific molecules secreted by each strain can vary. Additionally, phenotypic analysis indicates that regulation of activities (e.g. enzymes and motility) differs among strains.ConclusionsThe analyses presented here demonstrate that while general mechanisms by which X. bovienii bacterial strains interact with their invertebrate hosts are similar, the specific molecules mediating these interactions differ. Our data support that adaptation of individual bacterial strains to distinct hosts or niches has occurred. For example, diverse metabolic profiles among bacterial symbionts may have been selected by dissimilarities in nutritional requirements of their different nematode hosts. Similarly, factors involved in parasitism (e.g. immune suppression and microbial competition factors), likely differ based on evolution in response to naturally encountered organisms, such as insect hosts, competitors, predators or pathogens. This study provides insight into effectors of a symbiotic lifestyle, and also highlights that when mining Xenorhabdus species for novel natural products, including antibiotics and insecticidal toxins, analysis of multiple bacterial strains likely will increase the potential for the discovery of novel molecules.

Dataset Information

Steinernema poinari (Nematoda: Steinernematidae): a new symbiotic host of entomopathogenic bacteria Xenorhabdus bovienii.

Publications

Steinernema poinari (Nematoda: Steinernematidae): a new symbiotic host of entomopathogenic bacteria Xenorhabdus bovienii.

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