Cyanobacterial communities of the Sør Rondane Mountains (East Antarctica) differ by substrate types

Cyanobacteria of the Antarctic ice-free areas are ecosystem engineers due to their role as pri mary producers (Chrismas et al. 2018). Yet, cyanobacterial communities and their drivers within edaphic ecosystems of inland Antarctica are often overlooked. A previous study (Savaglia et al. 2024) describing microbial communities from around 100 soil samples of the western Sør Ron dane Mountains (East Antarctica) showed that substrate types were major structuring factors and several cyanobacterial phylotypes were recognized as putative keystone taxa. Here, cyanobac terial diversity was further investigated. Amplicon sequencing was applied using cyanobacterial
specific primers targeting the V3-V4 region of the 16S rRNA gene via the Illumina MiSeq platform and taxonomy was assigned using the CyanoSeq database. Our results confirmed that substrate types shape the cyanobacterial communities of this region, providing a higher taxonomic reso lution compared to our previous study. Granite harboured the greatest cyanobacterial diversity with a high abundance of filamentous cyanobacteria (i.e. Leptolyngbyaceae, Gomontiellaceae, Microcoleaceae, Oculatellaceae, Nostocaceae), and also unicellular taxa (Cyanothecaceae). In contrast, cyanobacterial diversity was lower in the other investigated substrate types, which were
often dominated by only one taxon. Specifically, marble was dominated by Alitarella, gneiss by Cyanothece, and the dry and oligotrophic Austkampane and Widerøefjellet moraines by Microco leaceae and Gomontiellaceae, respectively. Moreover, many taxa were uniquely encountered in the moraines of Yûboku-dani Valley, the only site characterized by the presence of several lakes, suggesting a high endemicity degree. Overall, our data highlight the importance of using specific primers and up-to-date taxonomy to accurately draw conclusions about microbial ecology.