Li, Wen‐Jun

Abstract Geothermal systems harbor abundant novel microorganisms, representing substantial phylogenetic and functional diversity among yet‐to‐be‐cultivated bacteria with significant ecological roles. Nevertheless, research on the diversity, metabolic potential, and evolutionary history of these uncultured taxa remains limited. In this study, 19 metagenome‐assembled genomes (MAGs) were recovered from hot springs in Tengchong, Yunnan Province. Phylogenetic analyses indicate that these MAGs form sister lineages to an existing clade, leading to their proposed classification within three novel phyla: Yinglongibacterota , Xuanmingibacterota , and Gonggongibacterota , named after figures from the traditional Chinese legend, Classics of Mountains and Seas. Sequence analysis of both hot spring‐derived and published MAGs reveals that all three phyla exhibit similar facultative anaerobic lifestyles. Multiple substrates, including cellulose, glucan, pectin, and xylan, can be degraded by these phyla, especially Gonggongibacterota , suggesting their critical role in converting complex plant matter into more readily degradable substrates and contributing to sugar fermentation. Furthermore, the ability of these phyla to reduce selenite facilitates environmental detoxification. Notably, gene loss events have resulted in widespread auxotrophy for heme and biotin in these lineages, which may indicate microbial cross‐feeding in the community as an adaptation strategy. These pioneering results provide a comprehensive overview of the taxonomic and metabolic characteristics of the three novel phyla, offering insights into their ecological significance and guiding future cultivation efforts.

Abstract Sci.sci.o.nel'la. N.L. fem. dim. n. Sciscionella arbitrary name formed from the acronym of the South China Sea Institute of Oceanology, SCISCIO, where taxonomic studies on this taxon were performed. The genus Sciscionella is classified as a member of the family Pseudonocardiaceae , order Pseudonocardiales , and in the class Actinobacteria . The member of this genus has a 16S rRNA sequence identity of less than 94% with the other members of the family Pseudonocardiaceae . In the phylogenetic tree based on 16S rRNA gene sequences, the single member of this genus, Sciscionella marina , forms a distant clade, closely related to the genera Haloechinothrix, Thermocrispum , and Yuhushiella . Cells are characterized with cell‐wall chemotype IV and phospholipid pattern type III sensu Lechevalier et al. 1977. The predominant respiratory quinone is MK‐9(H 4 ), and the fatty acid composition is dominated by saturated branched‐chain fatty acids, but not mycolic acids. Phenotypically, strains are aerobic and stain Gram‐positive. They could grow at 10–37°C, pH 6.0–8.0, and in the presence of up to 13% NaCl (w/v). The genus comprises one species, Sciscionella marina (the type species of the genus). DNA G + C content (mol%) : 68 (WGS). Type species : Sciscionella marina Tian, Zhi, Qiu, Zhang, Tang, Xu et al. 2009, 225 VP . Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Sciscionella is: correct name (last update, February 2025) * . LPSN classification: Bacteria / Bacillati / Actinomycetota / Actinomycetes / Pseudonocardiales / Pseudonocardiaceae / Sciscionella The genus Sciscionella can also be recovered in the Genome Taxonomy Database (GTDB) as g__Sciscionella (version v220) ** . GTDB classification: d__Bacteria / p__Actinomycetota / c__Actinomycetes / o__Mycobacteriales / f__Pseudonocardiaceae / g__Sciscionella * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776