TITLE:  Researchers Find Organism They Can Really Relate To
      AUTHOR:  HOFFMAN, MICHELE
     JOURNAL:  Science
    CITATION:  July 3, 1992, 256(5066): 32.
        YEAR:  1992
    PUB TYPE:  Article
 IDENTIFIERS:  EVOLUTIONARY BIOLOGY; EOCYTES; EUKARYOTES; ARCHAEBACTERIA; 
               PALEONTOLOGY; MOLECULAR EVOLUTION; RELATEDNESS
    ABSTRACT:       Researchers at the University of California at Los 
               Angeles (UCLA) have found evidence that sulfur-metabolizing 
               organisms, or eocytes, that thrive in temperatures at or 
               above the boiling point of water are more closely related to 
               the cells of higher organisms than they are to other 
               bacteria. These findings, however, have created a rift in the 
               community of evolutionary biologists who have been trying to 
               figure out the ancestry of eukaryotes--a class of cells that 
               first evolved more than two billion years ago and whose 
               members now include the cells of all known plants and 
               animals, including humans.
                    Conventional wisdom holds that eukaryotes share a common 
               ancestor with all the arachaebacteria, a diverse bacterial 
               "superclass" whose members include methane-producing 
               methanogens, halophiles that dwell in highly salty 
               environments, and the sulfur-metabolizing eocytes. Other 
               researchers had concluded, based on analyses of genes that 
               code for RNA in ribosomes, that the arachaebacteria are all 
               closely related to each other, and, as a group, are more 
               closely related to eukaryotes than they are to eubacteria. 
               But electron microscope analyses conducted by the UCLA 
               scientists indicated instead that "ecoytes are the closest 
               relative to eukaryotes."
                    Many other evolutionary biologists, however, remain 
               skeptical; one argues that one cannot always infer family 
               ties from the presence or absence of a protein sequence. In 
               fact, one evolutionary biologist found deletions of protein 
               sequences that gave misleading information in trying to trace 
               the relatedness of a group of bacteria. The UCLA scientists 
               counter that, in cases of random insertion and deletion of 
               sequences, one would not expect to see the insertion in all 
               eukaryotes and eocytes.
                    Still other researchers are concerned that data from one 
               protein are not sufficient to build a whole argument about 
               relatedness, and that the one selected is the wrong molecule 
               to analyze. In fact, they assert, if a different but related 
               molecule that is longer is analyzed, the results support the 
               conventional theory that the arachaebacteria are all closely 
               related. Ultimately, researchers will have to learn more 
               about the organization of genomes, and how it changes over 
               time.