Biogeography and Phylogeny of Aigarchaeota, A Novel Phylum of Archaea

摘要

‘Aigarchaeota’ is a candidate phylum of Archaea known only by 16S rRNA gene fragments from cultiva­tion-independent microbial surveys and a single composite genome from Candidatus ‘Caldiarchaeum sub­terraneum’, an inhabitant of a subterranean gold mine in Japan. Gene sequences associated with ‘Aigarchaeo­ta’ have been found in a variety of geothermal habits, however a comprehensive analysis of the phylogeny and distribution of ‘Aigarchaeota’ has not yet been done. Public databases were mined for 16S rRNA gene sequences related to known ‘Aigarchaeota’ and a combination of approaches were used to rigorously define the phylogenetic boundaries of the phylum, investigate its distribution, and design potential ‘Aigarchaeota’- specific primers. Approximately 300 16S rRNA genes and gene fragments affiliated with ‘Aigarchaeota’ were identified, phylogenic analyses suggested that ‘Aigarchaeota’ belonged to at least three family- to order-level groups and at least 13 genus-level groups, and supported the proposed relationship between ‘Aigarchaeota’, Thaumarchaeota, Crenarchaeota, and Korarchaeota in the so-called ‘TACK’ superphylum. A global distri­bution was suggested with genus-level group habitat differentiation. Some groups were predominantly ter­restrial (1A, 2B, 3, 4 u26 5) while other groups were mostly found in Marine habitats (6-8). Fifteen strong ‘Ai­garchaeota’-specific primer candidates for the polymerase chain reaction (PCR) amplification of 16S rRNA genes were designed for further analyses.