In vivotranscriptome analysis provides insights into host-dependent expression of virulence factors byYersinia entomophagaMH96, during infection ofGalleria mellonella

Abstract

The function of microbes can be inferred from knowledge of genes specifically expressed in natural environments. Here we report the in vivo transcriptome of the entomopathogenic bacterium Yersinia entomophaga MH96, captured during three stages of intrahemocoelic infection in Galleria mellonella. A total of 1,285 genes were significantly upregulated by MH96 during infection; 829 genes responded to in vivo conditions during at least one stage of infection, 289 responded during two stages of infection and 167 transcripts responded throughout all three stages of infection. Genes upregulated during the earliest infection stage included components of the insecticidal toxin complex Yen-TC (chi1, chi2 and yenC1), genes for rearrangement hotspot element containing protein yenC3, cytolethal distending toxin cdtAB and vegetative insecticidal toxin vip2. Genes more highly expressed throughout the infection cycle included the putative heat-stable enterotoxin yenT and three adhesins (usher-chaperone fimbria, filamentous hemagglutinin and an AidA-like secreted adhesin). Clustering and functional enrichment of gene expression data also revealed expression of genes encoding type III and VI secretion system-associated effectors. Together these data provide insight into the pathobiology of MH96 and serve as an important resource supporting efforts to identify novel insecticidal agents.

Lysis cassette-mediated exoprotein release inYersinia entomophagais controlled by a PhoB- like regulator

“…Based on the role of RoeA in the transcription of exoproteins including the Yen-Tc and the effect of temperature on virulence regulation in vitro (35) and in vivo in G. mellonella at 25°C and 37°C (15), we investigated the effect of temperature on the translation of RoeA and the Yen-Tc associated Chi1, as an exoprotein proxy.…”

“…Unless stated, cultures were incubated with shaking at 250 rpm in a Ratek model OM11 orbital incubator. Antibiotic concentrations used were (µg mL -1 ): E. coli, kanamycin (50), ampicillin (100); Y. entomophaga, kanamycin (100); spectinomycin (100), chloramphenicol (90), tetracycline (15).…”

“…The broad host range entomopathogen Y. entomophaga strain MH96 encodes multiple virulence factors including adhesins, Type 3 and Type 6 secretion systems, proteolytic enzymes, and insecticidal toxins (14). Many of these virulence genes are upregulated during haemocoelic infection of Galleria mellonella at 25°C (15). In Lauria Bertani (LB) broth at temperatures of ≤ 25°C Y. entomophaga releases large quantities of exoprotein including the Yen-Tc (16).The production of exoprotein is elevated through exponential growth and decreases through stationary phase (17).…”