TITLE:  'Rare' Bug Dominates the Oceans
      AUTHOR:  HECHT, JEFF
     JOURNAL:  New Scientist
    CITATION:  November 19, 1994, 44(1952): 21.
        YEAR:  1994
    PUB TYPE:  Article
 IDENTIFIERS:  BACTERIA; MICROBIOLOGY; MARINE ECOLOGY; PROKARYOTES; 
               ARCHAEBACTERIA
    ABSTRACT:       A group of unusual microorganisms, best known for their 
               ability to exist in extreme conditions, is far more 
               widespread than biologists once thought. Archaebacteria, far 
               from being an evolutionary curiosity, may play an important 
               role in marine and global ecology.
                    Edward DeLong of the University of California at Santa 
               Barbara, has found the organisms in the cold waters along the 
               Antarctic coast, where they provide up to 30% of the single-
               celled marine biomass. He has also found them in significant 
               numbers at the cold depths below 100 m in temperate oceans.
                    Archaebacteria, now generally classified within the 
               taxon Archaea, lack nuclei, which puts them among the 
               prokaryotes. Biologists initially assumed they were closely 
               related to the other prokaryotes--typical bacteria and the 
               blue-green algae. The first archaebacteria recognized by 
               scientists had unusual metabolisms. Some generated methane, 
               while others lived in deep-sea vents or in hot or saline 
               waters.
                    Early speculation held that archaebacteria were 
               extremely primitive types which had survived since the early 
               days of life on Earth. This view changed when later studies 
               showed that archaebacteria are genetically very distant from 
               other prokaryotes, and closer to the more complex nucleated 
               cells called eukaryotes, which include all the higher plants 
               and animals. Biologists still considered archaebacteria to be 
               rare, however.
                    In his new study, DeLong looked for sequences of 
               ribosomal RNA that were characteristic of archaebacteria and 
               other single-celled organisms. He avoided using the standard 
               techniques of DNA amplification because these might not 
               amplify all sequences uniformly.
                    He found that the highest concentrations of 
               archaebacteria were in the Antarctic--between 18.5 and 30.5%. 
               But his group also found that they reached more than 10% in 
               the sea off Santa Barbara, between 100 and 500 m down. The 
               scientists also detected archaebacteria in the Arctic, the 
               Mediterranean, and the Baltic Sea.
                    The abundance of archaebacteria is only one surprise. 
               The new discoveries include two distinct deep-sea lineages, 
               one related to types that grow in hot water, the other to 
               methane-generators. Although no one has cultured the new 
               types yet, DeLong says they must have been growing in cold, 
               oxygenated environments quite unlike the homes of their 
               relatives.