The bacterial microbiomes of the centipede Lithobius forficatus (Chilopoda, Lithobiomorpha) are complex and environmentally influenced

Abstract Once thought to be sterile, animal venom systems instead harbour diverse microbiomes. In some venomous lineages, bacteria contribute to venom production, while in other lineages bacteria have donated venom toxin genes via horizontal gene transfer. We studied the centipede Lithobius forficatus to shed new light on these topics. L. forficatus has an anterior venom-producing system comprising forcipules and associated venom glands, as well as a serially homologous secretory defence system comprising its posterior legs and associated telopodal glands. We used full-length 16S rRNA sequencing to characterise the bacterial microbiomes of these weaponised appendages, and of gonads and habitat soil. We found that all centipede organs harboured diverse microbiomes that overlapped substantially with soil microbiomes, with no differences between the microbiomes of male and female centipedes. While alpha diversity analysis identified significant differences in observed diversity between sample types, beta diversity analysis only identified a significant difference in microbiomes of different geographic locations. The gonads (only internal organ sample) contained the smallest number of unique bacterial operational taxonomic units and lacked a core microbiome. Finally, there was no evidence to suggest that the bacterial microbiomes directly contribute toxins to the weaponised secretions of L. forficatus .