Exploration of firefly microbiomes

Fireflies are iconic insects but are threatened worldwide. Despite the urgent need to understand their biology to better conserve them, it remains unclear whether some firefly species harbor a stable microbiome. In addition, the potential benefits provided by microbes to firefly hosts have never been evaluated. Bioluminescent fireflies require precursors of key enzymatic substrates and energy supplies to fuel light emission, and bacterial symbionts could conceivably participate in such demanding tasks. Previous studies show that Mollicutes bacteria are common associates of these insects. We thus hypothesized that several firefly species partner with members of the Mollicutes which provide benefits to firefly hosts. In a pilot study, we characterized the microbiome of 19 firefly specimens (six species from three genera) using 16S rRNA amplicon sequencing and analyzed the evolution and functions encoded in seven firefly-isolated Mollicutes genomes. We found that bacterial community profiles differ across firefly genera. Bacterial variants from the Williamsoniiplasma genus (Mollicutes) are prevalent and abundant among common bioluminescent Lampyrinae species (Photinus pyralis and Pyractomena borealis). Firefly-associated Williamsoniiplasma have conserved the genomic ability to utilize extracellular arbutin in the production of hydroquinone, which is a precursor of luciferin, the substrate of bioluminescence. Building upon these preliminary results, we intend to conduct a more comprehensive microbiome survey across firefly lineages and sequence firefly-associated metagenomes/metatranscriptomes. Through this research, we will infer the stability of bacterial associations in fireflies, ascertain firefly dependency upon microbial symbionts and evaluate the role such partners may play in firefly biology.