# Comparison of Xenorhabdus bovienii bacterial strain genomes reveals diversity in symbiotic functions

## TL;DR

This study compares the genomes of 10 Xenorhabdus bovienii strains to understand how they differ in their ability to interact with insect hosts and nematode partners.

## Contribution

The study reveals strain-specific diversity in symbiotic functions and secreted molecules within a single bacterial species.

## Key findings

- X. bovienii strains share general host-interaction mechanisms but differ in specific genes and secreted molecules.
- Genomic and phenotypic variation among strains suggests adaptation to distinct hosts or ecological niches.
- Diversity in metabolic and parasitic factors may result from evolutionary responses to different environmental pressures.

## Abstract

Xenorhabdus 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.

To 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.

The 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.

The 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

The online version of this article (doi:10.1186/s12864-015-2000-8) contains supplementary material, which is available to authorized users.