2012 年 46 巻 2 号 p. 113-128
Since the first classification by Woese and Fox (1977), Archaea, one of three domains of life, had been originally believed to exist in extreme environments including high temperature, high salinity, low oxygen concentration. However, recent advances in molecular and phylogenic approaches revealed their widespread distribution in marine and terrestrial environment including deep subsurface biosphere. The planktonic and benthic archaeal assemblages include two major phyla Euryarchaeota and Crenarchaeota. The novel phylum have been also proposed recently as Thaumarchaota, Korarchaota, and Nanoarchaeota. To elucidate unknown archaeal ecology, we evaluated intra-molecular isotopic composition to focus into archaeal membrane lipid biosynthesis using 13C-tracing techniques. The novel molecular diagnosis showed heterogenous 13C-incorporation driven by salvage (recycling) and de novo pathways in energy-limited environment such as deep-sea environments. Here, we reviewed the recent knowledge of prokaryotic ecology and biogeochemistry from intra-molecular isotopic signatures.
