- PM1072 - Bistability and antimicrobial peptide resista nce in the entomopathogenic bacteria Photorhabdus

- PM1072 - Bistability and antimicrobial peptide resista nce in the entomopathogenic bacteria Photorhabdus. International Union of Microbiological Societies Congresses - IUMS201

DNA Adenine Methyltransferase (Dam) plays a role in Photorhabdus luminescens motility and virulence in insects

DNA Adenine Methyltransferase (Dam) plays a role in Photorhabdus luminescens motility and virulence in insects. Congrès de la Société Française de Microbiologie (SFM

Dam overexpression increases biofilms formation but impairs motility and pathogenicity of Photorhabdus luminescens

Dam overexpression increases biofilms formation but impairs motility and pathogenicity of Photorhabdus luminescens. 7. congress of European Microbiologists FEMS 201

Phenotypic switching in Xenorhabdus: some hints on how and why

Phenotypic switching in Xenorhabdus: some hints on how and why. Réseau Ecologie des Interactions Durables (REID

A New Member of the Growing Family of Contact-Dependent Growth Inhibition Systems in Xenorhabdus doucetiae

Xenorhabdus is a bacterial symbiont of entomopathogenic Steinernema nematodes and is pathogenic for insects. Its life cycle involves a stage inside the insect cadaver, in which it competes for environmental resources with microorganisms from soil and the insect gut. Xenorhabdus is, thus, a useful model for identifying new interbacterial competition systems. For the first time, in an entomopathogenic bacterium, Xenorhabdus doucetiae strain FRM16, we identified a cdi-like locus. The cdi loci encode contact-dependent inhibition (CDI) systems composed of proteins from the two-partner secretion (TPS) family. CdiB is the outer membrane protein and CdiA is the toxic exoprotein. An immunity protein, CdiI, protects bacteria against inhibition. We describe here the growth inhibition effect of the toxic C-terminus of CdiA from X. doucetiae FRM16, CdiA-CTFRM16, following its production in closely and distantly related enterobacterial species. CdiA-CTFRM16 displayed Mg2+-dependent DNase activity, in vitro. CdiA-CT (FRM16)-mediated growth inhibition was specifically neutralized by CdiI(FRM16). Moreover, the cdi(FRM16) locus encodes an ortholog of toxin-activating proteins C that we named CdiC(FRM16). In addition to E. coli, the cdiBCAI-type locus was found to be widespread in environmental bacteria interacting with insects, plants, rhizospheres and soils. Phylogenetic tree comparisons for CdiB, CdiA and CdiC suggested that the genes encoding these proteins had co-evolved. By contrast, the considerable variability of CdiI protein sequences suggests that the cdiI gene is an independent evolutionary unit. These findings further characterize the sparsely described cdiBCAI-type locus

Prolonged culture and long lasting infections select for poorly transmitted bacterial variants

Prolonged culture and long lasting infections select for poorly transmitted bacterial variants. MicrobiOccitanie 2019- Rencontre des Microbiologistes Région Occitani

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

Changes in rearing conditions rapidly modify gut microbiota structure in <em>Tenebrio molitor</em> larvae

The gut microbiota of multicellular organisms has been shown to play a key role in their host biology. In mammals, it has an invariant component, responsible for establishing a mutualistic relationship with the host. It also contains a dynamic fraction which facilitates adaptation in response to changes in the environment. These features have been well described in mammals, but little is known about microbiota stability or plasticity in insects. We assessed changes in microbiota composition and structure in a reared insect after a change in rearing conditions. We reared Tenebrio molitor (Coleoptera, Tenebrioninae) larvae for five days in soil samples from two river banks and analyzed their gut microbial communities by a metabarcoding technique, using the V3-V4 region of the 16S rRNA gene and the housekeeping gene gyrB. We found that soil-reared insects had a significantly more diverse microbiota than the control insects and that insects reared in soil from different sites had significantly different microbiota. We confirmed this trend by absolute quantification of the two mains fluctuating taxonomic groups: the Enterobacteriaceae family and the Pseudomonas genus, dominant in the soil-reared insects and in the control insects, respectively. Our results suggest the existence of a resident microbiota in T. molitor gut, but indicate that rearing changes can induce rapid and profound changes in the relative abundance of some of the members of this resident microbiota

FliZ is a global regulatory protein affecting the expression of flagellar and virulence genes in individual Xenorhabdus nematophila bacterial cells

Heterogeneity in the expression of various bacterial genes has been shown to result in the presence of individuals with different phenotypes within clonal bacterial populations. The genes specifying motility and flagellar functions are coordinately regulated and form a complex regulon, the flagellar regulon. Complex interplay has recently been demonstrated in the regulation of flagellar and virulence gene expression in many bacterial pathogens. We show here that FliZ, a DNA-binding protein, plays a key role in the insect pathogen, Xenorhabdus nematophila, affecting not only hemolysin production and virulence in insects, but efficient swimming motility. RNA-Seq analysis identified FliZ as a global regulatory protein controlling the expression of 278 Xenorhabdus genes either directly or indirectly. FliZ is required for the efficient expression of all flagellar genes, probably through its positive feedback loop, which controls expression of the flhDC operon, the master regulator of the flagellar circuit. FliZ also up- or downregulates the expression of numerous genes encoding non-flagellar proteins potentially involved in key steps of the Xenorhabdus lifecycle. Single-cell analysis revealed the bimodal expression of six identified markers of the FliZ regulon during exponential growth of the bacterial population. In addition, a combination of fluorescence-activated cell sorting and RT-qPCR quantification showed that this bimodality generated a mixed population of cells either expressing ("ON state") or not expressing ("OFF state") FliZ-dependent genes. Moreover, studies of a bacterial population exposed to a graded series of FliZ concentrations showed that FliZ functioned as a rheostat, controlling the rate of transition between the "OFF" and "ON" states in individuals. FliZ thus plays a key role in cell fate decisions, by transiently creating individuals with different potentials for motility and host interactions

DNA Adenine Methyltransferase (Dam) Overexpression Impairs Photorhabdus luminescens Motility and Virulence

Dam, the most described bacterial DNA-methyltransferase, is widespread in gamma-proteobacteria. Dam DNA methylation can play a role in various genes expression and is involved in pathogenicity of several bacterial species. The purpose of this study was to determine the role played by the dam ortholog identified in the entomopathogenic bacterium Photorhabdus luminescens. Complementation assays of an Escherichia coli dam mutant showed the restoration of the DNA methylation state of the parental strain. Overexpression of dam in P. luminescens did not impair growth ability in vitro. In contrast, compared to a control strain harboring an empty plasmid, a significant decrease in motility was observed in the dam-overexpressing strain. A transcriptome analysis revealed the differential expression of 208 genes between the two strains. In particular, the downregulation of flagellar genes was observed in the dam-overexpressing strain. In the closely related bacterium Xenorhabdus nematophila, dam overexpression also impaired motility. In addition, the dam-overexpressing P. luminescens strain showed a delayed virulence compared to that of the control strain after injection in larvae of the lepidopteran Spodoptera littoralis. These results reveal that Damplays amajor role during P. luminescens insect infection