Panguiarchaeum symbiosum, a potential hyperthermophilic symbiont in the TACK superphylum

The biology of Korarchaeia remains elusive due to the lack of genome representatives. Here, we reconstruct 10 closely related metagenome-assembled genomes from hot spring habitats and place them into a single species, proposed herein as Panguiarchaeum symbiosum. Functional investigation suggests that Panguiarchaeum symbiosum is strictly anaerobic and grows exclusively in thermal habitats by fermenting peptides coupled with sulfide and hydrogen production to dispose of electrons. Due to its inability to biosynthesize archaeal membranes, amino acids, and purines, this species likely exists in a symbiotic lifestyle similar to DPANN archaea. Population metagenomics and metatranscriptomic analyses demonstrated that genes associated with amino acid/peptide uptake and cell attachment exhibited positive selection and were highly expressed, supporting the proposed proteolytic catabolism and symbiotic lifestyle. Our study sheds light on the metabolism, evolution, and potential symbiotic lifestyle of Panguiarchaeum symbiosum, which may be a unique host-dependent archaeon within the TACK superphylum. [Display omitted] •Panguiarchaeum symbiosum belongs to a previously unknown order within the Korarchaeia•P. symbiosum has a symbiotic lifestyle by fermenting peptides and reducing sulfur•Genes related to proteolytic catabolism and cell attachment exhibit positive selection•Genes related to proteolytic catabolism and cell attachment are highly expressed Qu et al. report 10 closely related genomes from hot springs with the name Panguiarchaeum symbiosum proposed. By focusing on ecological niches and evolution, they reveal a symbiotic lifestyle of these microbes, where genes associated with nutrient acquisition and cell attachment are prone to be positively selected and highly transcribed.