The microbiome of Antarctica's endemic chironomid midge: from general microbial community to endosymbiotic bacteria

BackgroundThe interactions between the host organism and the microbiota play an important role in the hosts survival, influencing its physiology and adaptation. The Antarctic, due to its extreme living conditions, is a unique region for studying such interactions. However, research on the microbiomes of Antarctic terrestrial and freshwater invertebrates remains limited, especially with regard to the regions sole endemic insect, Belgica antarctica. Our aim was to study the B. antarctica microbiome collected from different substrates and from varying ornithogenic influence levels. MethodsA total of 330 B. antarctica larvae and moss substrates were sampled at three sites with different ornithogenic impact, followed by DNA extraction using Qiagen kits. The V3-V4 region of bacterial 16S rRNA was amplified by PCR and sequenced on the Illumina NovaSeq platform, followed by bioinformatic processing in QIIME2 for OTU clustering, taxonomic classification, and diversity analysis. Further analysis and visualization was performed in R, Python and GraphPad Prism. ResultsAmplicon sequencing revealed rich microbial diversity, with NMDS demonstrating clear clustering of samples according to their origin (insects vs substrate) and ornithogenic influence level. Comparative analysis revealed that the vast majority of OTUs associated with B. antarctica (ca. 95%) were shared with substrates, whereas the insect-specific fraction was small, highly variable, and partially influenced by moss species. Ornithogenic influence significantly structured the symbiotic microbiota in both insects and substrates, reducing microbial diversity and altering the relative abundance of major bacterial taxa. Overall, substrate type and ornithogenic impact are significant factors influencing microbial community structure, while insect-specific taxa formed only a minor, heterogeneous component of this midge microbiome. Additionally, the Wolbachia infection was detected in B. antarctica larvae for the first time. ConclusionThe substrate that B. antarctica inhabits, as well as ornithogenic influence, play a significant role in the shaping of the species microbiome. This Antarctic chironomid also maintains a core microbial community. The detection of Wolbachia in B. antarctica is the first evidence of this endosymbiont in Antarctica.