16S RIBOSOMAL-RNA SEQUENCES REVEAL NUMEROUS UNCULTURED MICROORGANISMS IN A NATURAL COMMUNITY

MICROBIOLOGISTS have been constrained in their efforts to describe the compositions of natural microbial communities using traditional methods. Few microorganisms have sufficiently distinctive morphology to be recognized by microscopy. Culture-dependent methods are biased, as a microorganism can be cultivated only after its physiological niche is perceived and duplicated experimentally. It is therefore widely believed that fewer than 20% of the extant microorganisms have been discovered1,2, and that culture methods are inadequate for studying microbial community composition3-7. In view of the physiological and phylogenetic diversity among microorganisms8, speculation that 80% or more of microbes remain undiscovered raises the question of how well we know the Earth's biota and its biochemical potential. We have performed a culture-independent analysis of the composition of a well-studied hot spring microbial community, using a common but distinctive cellular component, 16S ri bosom al RNA. Our results confirm speculations about the diversity of uncultured microorganisms it contains. © 1990 Nature Publishing Group.