The newly proposed TACK and DPANN archaea detected in the production waters from a high-temperature petroleum reservoir

Revealing the diversity and distribution of archaea is basically crucial to understanding their ecological functions in subsurface petroleum reservoir ecosystems. However, the knowledge about the abundance and distribution of newly proposed archaea (e.g. TACK and DPANN superphyla) in such environments is still limited. In the present work, archaeal communities from five production wells of a high-temperature petroleum reservoir were characterized by high-throughput sequencing. The outcome showed that in the five samples over 98% of archaeal sequences were affiliated to Euryarchaeota, and the rest belonged to newly proposed archaeal phyla (Thaumarchaeota, Verstraetearchaeota, Bathyarchaeota, Aigarchaeota and Woesearchaeota). Based on the defined criteria of rare taxa (< 0.1%), OTUs affiliated within Bathyarchaeota, Thaumarchaeota and Woesearchaeota were mostly present as the rare biosphere in the samples. The archaeal communities were significantly shaped by different geochemical parameters of the production waters from the petroleum reservoir. The co-occurrence network analysis revealed the potential syntrophic interactions among the archaea themselves in the subterrestrial environments. Our results indicate that the newly proposed archaea are ubiquitous, also present in the petroleum reservoirs, where they contribute to the ecosystem diversity and play potential roles in the biogeochemical cycle of carbon. This work also provides an overall understanding of the identity, ecology, and functional diversity of newly proposed archaea in petroleum reservoirs.