Background Extreme environments are useful systems to investigate limits of life, microbial biogeography and ecology, and the adaptation and evolution of microbial lineages. Many novel microbial lineages have been discovered in extreme environments, especially from the Planctomycetota–Verrucomicrobiota–Chlamydiota (PVC) superphyla. However, their evolutionary history and roles in ecosystem functioning and microbiome assemblage are poorly understo [...]