Ökologische Relevanz und molekulare Regulation von Antibiotika-produzierenden bakteriellen Symbionten in Lagriinae Käfer

• Antragsteller: Professor Dr. Martin Kaltenpoth, seit 4/2021
• Fachliche Zuordnung: Ökologie und Biodiversität der Tiere und Ökosysteme, Organismische Interaktionen ; Mikrobielle Ökologie und Angewandte Mikrobiologie ; Systematik und Morphologie der Tiere
• Förderung: Förderung von 2019 bis 2022
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 416606594

• Erstellungsjahr: 2023

Zusammenfassung der Projektergebnisse

Symbiotic interactions with microorganisms are a driving force in the evolution of multicellular organisms. Along with nutritional symbioses, those with a defensive basis are frequent in nature, yet less is known about their ecology and evolution, especially under natural conditions. Lagriinae beetles engage in a symbiosis with multiple strains of Burkholderia gladioli bacteria, which are transmitted from mother to offspring and can protect the host eggs from antagonistic fungi. Recent findings show that co-existing symbiont strains can each produce a distinct set of bioactive secondary metabolites with antimicrobial activities. Using this model system, our aim was to better understand the ecology, evolution and molecular basis of defensive symbiosis. The first part of the project focused on the ecological relevance of symbiont-mediated defense during host development and across Lagriinae species. Using a combination of analytical chemistry, mass-spectrometry imaging, fluorescence insitu hybridization (FISH) and manipulative bioassays, we demonstrated that Burkholderia provide protection to the beetles that extends beyond the eggs stage and across larval and pupal development, shielding in particular the vulnerable post-molting phases of the larvae from fungal infections. Microscopy and micro-computed tomography revealed morphological adaptations for symbiont maintenance and translocation through metamorphosis, providing an explanation for how the symbiosis can be stably maintained over evolutionary timescales. A comparison of symbiont strain dynamics and function between two congeneric Lagria species uncovered functional similarity in both symbioses, but differences in prevalence and relative abundance of coexisting symbiont strains. In order to unravel the molecular factors underlying the establishment and maintenance of symbiosis, we genetically manipulated the culturable symbiont strain LvStA and used transposon-insertion sequencing as a genome-wide unbiased approach for identifying candidate genes essential for host colonization. This technique yielded 262 candidate colonization factors, including genes involved in flagellar motility, lipopeptide biosynthesis, stress response and iron metabolism. On the host side, transcriptome sequencing across developmental stages revealed an upregulation of immune-related genes in symbiotic vs. aposymbiotic beetles, suggesting an active cross-talk between the symbiotic partners. Our results contribute to the general understanding of animal-microbe interactions in the context of host protection and provide valuable insights on the evolution and stability of multi-strain symbiotic interactions.

Projektbezogene Publikationen (Auswahl)

• An endosymbiont’s journey through metamorphosis of its insect host. Proceedings of the National Academy of Sciences, 117(35), 20994-20996.
  Kaltenpoth, Martin
  
• Versatile and Dynamic Symbioses Between Insects andBurkholderiaBacteria. Annual Review of Entomology, 65(1), 145-170.
  Kaltenpoth, Martin & Flórez, Laura V.
  
• Biosynthesis of Sinapigladioside, an Antifungal Isothiocyanate from Burkholderia Symbionts. ChemBioChem, 22(11), 1920-1924.
  Dose, Benjamin; Niehs, Sarah P.; Scherlach, Kirstin; Shahda, Sophie; Flórez, Laura V.; Kaltenpoth, Martin & Hertweck, Christian
  
• Transmission of Bacterial Symbionts With and Without Genome Erosion Between a Beetle Host and the Plant Environment. Frontiers in Microbiology, 12 (2021, 9, 22).
  Wierz, Jürgen C.; Gaube, Paul; Klebsch, Dagmar; Kaltenpoth, Martin & Flórez, Laura V.
  
• Transposon-insertion Sequencing as a Tool to Elucidate Bacterial Colonization Factors in a <em>Burkholderia gladioli</em> Symbiont of <em>Lagria villosa</em> Beetles. Journal of Visualized Experiments (174).
  Ganesan, Ramya; Kaltenpoth, Martin & Flórez, Laura V.
  
• Bacterial ectosymbionts in cuticular organs chemically protect a beetle during molting stages. The ISME Journal, 16(12), 2691-2701.
  Janke, Rebekka S.; Kaftan, Filip; Niehs, Sarah P.; Scherlach, Kirstin; Rodrigues, Andre; Svatoš, Aleš; Hertweck, Christian; Kaltenpoth, Martin & Flórez, Laura V.
  
• How It All Begins: Bacterial Factors Mediating the Colonization of Invertebrate Hosts by Beneficial Symbionts. Microbiology and Molecular Biology Reviews, 86(4).
  Ganesan, Ramya; Wierz, Jürgen C.; Kaltenpoth, Martin & Flórez, Laura V.
  
• Morphological adaptation for ectosymbiont maintenance and transmission during metamorphosis in Lagria beetles. Frontiers in Physiology, 13 (2022, 8, 30).
  Janke, Rebekka S.; Moog, Safira; Weiss, Benjamin; Kaltenpoth, Martin & Flórez, Laura V.