Bacterial symbionts in darkling beetles

Lagria hirta is a polyphagous darkling beetle that occurs in central Europe and is one of only two of its genus found in the region. Morphological descriptions in this and other species of the subfamily (Lagriinae) highlighted the presence of specialized organs associated to the reproductive system of females, which were already thought to harbor symbiotic microorganisms. Bacteria-containing structures had also been observed in L. hirta larvae, exhibiting an unusual location and development, not described in any other beetle so far. We have recently identified these endosymbionts as Burkholderia (β-proteobacteria), a genus whose members can exploit a wide variety of ecological niches. Ranging from plant-mutualistic nitrogen fixators to animal pathogens, Burkholderia have become highly interesting for medical, agricultural and industrial fields.

Our research on the Burkholderia - L. hirta symbiosis aims to elucidate the complete transmission route of the bacteria along the life cycle of the host and to understand the possible role of each partner in the association. We are using molecular tools, as well as phenotypic and genomic approaches to characterize the symbiotic bacteria and compare them to free-living relatives. Manipulative experiments are also carried out to assess possible fitness effects of the symbionts on the host. Additionally, we are interested in exploring the evolutionary history of lagriid hosts and their bacterial symbionts to reveal possible co-evolutionary patterns.