Shlafstein, M. D. | Search bioRxiv

bioRxiv2026

Amplicon and metagenomic data from fumarole-associated geothermal features of Hawaii

The Hawaiian islands are among the most geologically and volcanically active places on Earth. While the Hawaiian Archipelago is known for its animal and plant diversity, much less is known about microbial diversity in the areas diverse habitats. In this study, we focused on steam vent associated biofilms found on the most volcanically active island of Hawai{square}i, also known as the Big Island. From 46 samples from various biofilms and associated features around fumaroles emitting water steam, we generated amplicon and metagenomic sequences. Amplicon data showed that Chloroflexota and Cyanobacteriota are the numerically dominant phyla in these biofilm communities. We constructed 363 non-redundant medium to high-quality metagenome-assembled genomes (MAGs) that are at least 70% complete and with less than 5% contamination. Ten MAGs belong in the domain Archaea, and 353 belong in the domain Bacteria. This dataset could provide valuable insights into microbial diversity and ecology around volcanic features in Hawai i and elsewhere.

microbiology↗

bioRxiv2026

Taxonomic Description of Uncultured Cyanobacteria from Extreme Habitats through Genome-Based Classification

Cyanobacteria form a morphologically and phylogenetically diverse group of oxygenic phototrophic bacteria inhabiting a wide range of environments, including extreme habitats such as hot springs and volcanic steam vents. Many lineages, particularly those from these extreme environments, remain uncultured and are known only from metagenome-assembled genomes (MAGs), limiting their integration into formal taxonomy. Analysis of 46 steam vent associated samples from Hawai i using 16S rRNA amplicon sequencing revealed that cyanobacteria dominate these communities. Gloeobacter kilaueensis dominated pit-like environments with low-light conditions, while Leptolyngbyaceae and other families are more dominant in structured soil and wall communities. We further reconstructed 38 high-quality cyanobacterial MAGs and incorporated them into a phylogenomic analysis comprising 343 cyanobacterial genomes, followed by genome-based comparisons against 9,026 reference genomes. This revealed eight novel species and one novel genus spanning five orders: Chroococcidiopsidales, Leptolyngbyales, Nostocales, Oculatellales, and Oscillatoriales. Following SeqCode guidelines, we provide the first formal taxonomic descriptions of cyanobacterial MAGs and propose guidelines for integrating genome-based and cultivated material. These findings highlight Hawaiian steam vents as hotspots of previously uncharacterized cyanobacterial diversity and underscore the importance of genome-based nomenclature.

genomics↗