Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

In vivo transcriptome of insect pathogen Yersinia entomophaga MH96. (#52)

Amber R Paulson 1 2 , Xue-Xian Zhang 3 , Paul B Rainey 1 4 5 , Maureen O'Callaghan 2 , Mark RH Hurst 2
  1. New Zealand Institute for Advanced Study, Massey University at Albany, Auckland, New Zealand
  2. Forage Science, AgResearch Limited, Lincoln, New Zealand
  3. Institute of Natural and Mathematical Sciences, Massey University at Albany, Auckland, New Zealand
  4. Microbial Population Biology, Max Planck Institute for Evolutionary biology, Plön, Germany
  5. Laboratoire de Génétique de l’Evolution, ESPCI ParisTech, Paris, France

Pathogenic bacteria have evolved specialized virulence factors (VFs) that enable entry and persistence within host tissues. Here we investigated the in vivo transcriptome of a novel insect pathogenic bacterium, Yersinia entomophaga MH96, to identify key virulence factors involved during different stages of infection (early, middle and late) and at different temperatures (25 and 37 °C) within the hemocoel of larval insect host, Galleria mellonella. Originally, Y. entomophaga was isolated from the cadaver of Costelytra giveni (Coleoptera: Scarabaeidae) larva, which is an endemic and notorious pasture pest of New Zealand. Development of Y. entomophaga as a biopesticide has proven consistent pathogenesis by per os challenge against C. giveni, as well as a wide range of coleopteran, lepidopteran, and orthopteran species. Additionally, a median lethal dose of at least three bacterial cells is sufficient to kill larvae of the greater wax moth G. mellonella within 4 days of injection with similar levels of mortality observed at both 25°C and 37°C. Here we use a novel method to enrich for pathogen transcriptional signal from extracellular Y. entomophaga within the hemolymph of G. mellonella. Sequencing results provided sufficient alignment of transcripts to the reference genome (9 – 91 %) enabling capture of the dynamic range of pathogen gene expression within the host. Striking temperature-dependent regulation was observed for several key VFs, including the insecticidal toxin complex (Yen-TC), type VI secretion system and flagellum, all of which were completely down-regulated at 37 °C compared to 25 °C. These data are driving focused investigations into the temperature-dependent regulation of Yen-TC as well as the characterization of RNA-binding proteins that were shown to be up-regulated during early infection and at 37 °C in the host. This work provides critical insight into the pathobiology and in vivo gene expression of a potentially important biopesticide.