Genomic comparison within Xenorhabdus bovienii species: the avirulent strain X. bovienii CS03 is characterized by its pseudogene content

Genomic comparison within Xenorhabdus bovienii species: the avirulent strain X. bovienii CS03 is characterized by its pseudogene content. 5. Journées des Doctorants SP

Entomopathogenic nematode/bacteria couples Steinernema sp. /Xenorhabdus bovienii: how can genomics help us to understand virulence variations?

Entomopathogenic nematode/bacteria couples Steinernema sp. /Xenorhabdus bovienii: how can genomics help us to understand virulence variations?. 5. Journée du réseau IM

Comparative genomics in the entomopathogenic genera Xenorhabdus and Photorhabdus: insight in the XaxAB binary cytolysin-encoding locus

Comparative genomics in the entomopathogenic genera [i]Xenorhabdus[/i] and [i]Photorhabdus[/i]: insight in the XaxAB binary cytolysin-encoding locus. 49. Annual Meeting of the Society for Invertebrate Patholog

Candidate Virulence Loci in the Pan-Genome of the Entomopathogenic Bacterium Xenorhabdus bovienii

Candidate Virulence Loci in the Pan-Genome of the Entomopathogenic Bacterium Xenorhabdus bovienii. SIP Annual Meetin

Comparative genomics between two Xenorhabdus bovienii strains highlights differential evolutionary scenarios within an entomopathogenic bacterial species

Bacteria of the genus Xenorhabdus are symbionts of soil entomopathogenic nematodes of the genus Steinernema. This symbiotic association constitutes an insecticidal complex active against a wide range of insect pests. Within Xenorhabdus bovienii species, the X. bovienii CS03 strain (Xb CS03) is nonvirulent when directly injected into lepidopteran insects, and displays a low virulence when associated with its Steinernema symbiont. The genome of Xb CS03 was sequenced and compared with the genome of a virulent strain, X. bovienii SS-2004 (Xb SS-2004). The genome size and content widely differed between the twostrains. Indeed,XbCS03had a large genomecontaining several specific loci involved in the inhibition of competitors, including a fewNRPS-PKS loci (nonribosomal peptide synthetases and polyketide synthases) producing antimicrobialmolecules. Consistently, Xb CS03 had a greater antimicrobial activity than Xb SS-2004. The Xb CS03 strain contained more pseudogenes than Xb SS-2004. Decay of genes involved in the hostinvasion and exploitation (toxins, invasins, or extracellular enzymes) was particularly important in Xb CS03. This may provide an explanation for the nonvirulence of the strain when injected into an insect host.We suggest that Xb CS03 and Xb SS-2004 followed divergent evolutionary scenarios to cope with their peculiar life cycle. The fitness strategy of Xb CS03 would involve competitor inhibition, whereas Xb SS-2004 would quickly and efficiently kill the insect host. Hence, Xenorhabdus strains would have widely divergent host exploitation strategies, which impact their genome structure

Xenorhabdus bovienii CS03, the bacterial symbiont of the entomopathogenic nematodeSteinernema weiseri, is a non-virulent strain against lepidopteran insects.

Xenorhabdus bacteria (γ-proteobacteria: Enterobacteriaceae) have dual lifestyles. They have a mutualistic relationship with Steinernema nematodes (Nematoda: Steinernematidae) and are pathogenic to a wide range of insects. Each Steinernema nematode associates with a specific Xenorhabdus species. However, a Xenorhabdus species can have multiple nematode hosts. For example, Xenorhabdus bovienii (Xb) colonizes at least nine Steinernema species from two different phylogenetic clades. The Steinernema-Xb partnership has been found in association with different insect hosts. Biological and molecular data on the Steinernema jollieti-Xb strain SS-2004 pair have recently been described. In particular, the Xb SS-2004 bacteria are virulent alone after direct injection into insect, making this strain a model for studying Xb virulence. In this study, we searched for Xb strains attenuated in virulence. For this purpose, we underwent infection assays with five Steinernema spp.- Xb pairs with two insects, Galleria mellonella (Lepidoptera: Pyralidae) and Spodoptera littoralis (Lepidoptera: Noctuidae). The S. weiseri-Xb CS03 pair showed attenuated virulence and lower fitness in S. littoralis in comparison to the other nematode-bacteria pairs. Furthermore, when injected alone into the hemolymph of G. mellonella or S. littoralis, the Xb CS03 bacterial strain was the only non-virulent strain. By comparison with the virulent Xb SS-2004 strain, Xb CS03 showed an increased sensitivity to the insect antimicrobial peptides, suggesting an attenuated response to the insect humoral immunity. To our current knowledge, Xb CS03 is the first non-virulent Xb strain identified. We propose this strain as a new model for studying the Xenorhabdus virulence

Genome Evolution of Bartonellaceae Symbionts of Ants at the Opposite Ends of the Trophic Scale

Many insects rely on bacterial symbionts to supply essential amino acids and vitamins that are deficient in their diets, but metabolic comparisons of closely related gut bacteria in insects with different dietary preferences have not been performed. Here, we demonstrate that herbivorous ants of the genus Dolichoderus from the Peruvian Amazon host bacteria of the family Bartonellaceae, known for establishing chronic or pathogenic infections in mammals. We detected these bacteria in all studied Dolichoderus species, and found that they reside in the midgut wall, that is, the same location as many previously described nutritional endosymbionts of insects. The genomic analysis of four divergent strains infecting different Dolichoderus species revealed genes encoding pathways for nitrogen recycling and biosynthesis of several vitamins and all essential amino acids. In contrast, several biosynthetic pathways have been lost, whereas genes for the import and conversion of histidine and arginine to glutamine have been retained in the genome of a closely related gut bacterium of the carnivorous ant Harpegnathos saltator. The broad biosynthetic repertoire in Bartonellaceae of herbivorous ants resembled that of gut bacteria of honeybees that likewise feed on carbohydrate-rich diets. Taken together, the broad distribution of Bartonellaceae across Dolichoderus ants, their small genome sizes, the specific location within hosts, and the broad biosynthetic capability suggest that these bacteria are nutritional symbionts in herbivorous ants. The results highlight the important role of the host nutritional biology for the genomic evolution of the gut microbiota-and conversely, the importance of the microbiota for the nutrition of hosts

Genomic comparison within Xenorhabdus bovienii species: the avirulent strain X. bovienii CS03 is characterized by its pseudogene content

Genomic comparison within Xenorhabdus bovienii species: the avirulent strain X. bovienii CS03 is characterized by its pseudogene content. 5. Congress of European Microbiologists (FEMS 2013

Attenuated virulence and genomic reductive evolution in the entomopathogenic bacterial symbiont species, Xenorhabdus poinarii

Bacteria of the genus Xenorhabdus are symbionts of soil entomopathogenic nematodes of the genus Steinernema. This symbiotic association constitutes an insecticidal complex active against a wide range of insect pests. Unlike other Xenorhabdus species, Xenorhabdus poinarii is avirulent when injected into insects in the absence of its nematode host. We sequenced the genome of the X. poinarii strain G6 and the closely related but virulent Xenorhabdus doucetiae strain FRM16. G6 had a smaller genome (500-700 kb smaller) than virulent Xenorhabdus strains and lacked genes encoding potential virulence factors (haemolysins, type 5 secretion systems, enzymes involved in the synthesis of secondary metabolites, toxin-antitoxin systems). The genomes of all the X. poinarii strains analysed here had a similar small size. We did not observe the accumulation of pseudogenes, insertion sequences or decrease in coding density usually seen as a sign of genomic erosion driven by genetic drift in host-adapted bacteria. Instead, genome reduction of X. poinarii seems to have been mediated by the excision of genomic blocks from the flexible genome, as reported for the genomes of attenuated free pathogenic bacteria and some facultative mutualistic bacteria growing exclusively within hosts. This evolutionary pathway probably reflects the adaptation of X. poinarii to specific host

Genomic comparison within Xenorhabdus genus: X. poinarii species characterized by a small genome and attenuated virulence toward insects

Genomic comparison within Xenorhabdus genus: X. poinarii species characterized by a small genome and attenuated virulence toward insects . 5. Congress of European Microbiologists (FEMS 2013