ISOLATION OF A HYPERTHERMOPHILIC ARCHAEUM PREDICTED BY IN-SITU RNA ANALYSIS

A variety of hyperthermophilic bacteria and archaea(1) have been isola ted from high-temperature environments by plating and serial dilutions (2). However, these techniques allow only the small percentage of orga nisms able to form colonies, or those that are predominant within envi ronmental samples, to be obtained in pure culture, Recently, in situ 1 6S ribosomal RNA analyses of samples from the Obsidian hot pool at Yel lowstone National Park, Wyoming, revealed a variety of archaeal sequen ces, which,were all different from those of previously isolated specie s(3,4). This suggests substantial diversity of archaea with so far unk nown morphological, physiological and biochemical features, which may play an important part within high-temperature ecosystems, Here we des cribe a procedure to obtain pure cultures of unknown organisms harbour ing specific 16S rRNA sequences identified previously within the envir onment, It combines visual recognition of single cells by phylogenetic staining(5-9) and cloning by 'optical tweezers'(10,11). Our result va lidates polymerase chain reaction data on the existence of large archa eal communities.