MOLECULAR PHYLOGENY OF ARCHAEA FROM SOIL

Cultivation methods have contributed to our present knowledge about th e presence and diversity of microbes in naturally occurring communitie s. However, it is well established that only a small fraction of proka ryotes have been cultivated by standard methods and, therefore, the pr okaryotes that are cultivated may not reflect the composition and dive rsity within those communities. Of the two prokaryotic phylogenetic do mains, Bacteria and Archaea, members of the former have been shown to be ubiquitous in nature, with ample evidence of vast assemblages of un cultured organisms, There is also now increasingly compelling evidence that the Archaea, which were once thought to occupy a limited number of environments, are also globally widespread, Here we report the use of molecular phylogenetic techniques, which are independent of microbi al cultivation, to conduct an assessment of Archaea in a soil microbia l community, Small subunit ribosomal RNA genes of Archaea were amplifi ed from soil and cloned. Phylogenetic and nucleotide signature analyse s of these cloned small subunit ribosomal RNA gene sequences revealed a cluster of Archaea from a soil microbial community that diverge deep ly from the crenarchaeotal line of descent and has the closest affilia tion to the lineage of planktonic Archaea, The identification and phyl ogenetic classification of this archaeal lineage from soil contributes to our understanding of the ecological significance of Archaea as a c omponent of microbial communities in non-extreme environments.