Global approaches to understanding the secondary metabolism of entomopathogens

Speaker: Dr. Nicholas Tobias, Goethe University, Frankfurt, Germany
Host: Postdoc Victoria Challinor, Centre for Social Evolution (CSE)

Abstract:  Photorhabdus and Xenorhabdus bacteria are mutualistic symbionts of Heterorhabditis and Steinernema nematodes, respectively. These two symbiotic associations have independently converged on similar lifestyles. Their lifestyle involves an insect pathogenic phase, during which the nematodes seek out and infect insects, releasing the bacteria into the insect haemocoel, where they produce a variety of compounds that suppress the insect immune response, kill the insect and allow the nematodes to fully develop and replicate. Once the nutrients of the insect cadaver are depleted, the nematodes reacquire the bacteria and seek new prey. The secondary metabolism of the bacteria is key to each of these events and is underpinned by regulation via Hfq, an RNA chaperone and small RNAs. The regulation of these clusters was explored using RNAseq of knockout strains in Photorhabdus and key genomic elements common across the genera were identified through sequencing and ortholog clustering of 27 different species. Comparing the DNA sequences of biosynthetic gene clusters was unfortunately insufficient to identify related compounds in the different genera. However, high-throughput profiling using high-resolution mass spectrometry and molecular network analyses highlighted key structural similarities and identified new families of compounds produced by these bacteria, illuminating potentially essential elements and providing clues to the genetic sequences responsible for biosynthesis of these compounds.