WIDESPREAD ARCHAEA AND NOVEL BACTERIA FROM THE DEEP-SEA AS SHOWN BY 16S-RIBOSOMAL-RNA GENE-SEQUENCES

Marine microbial diversity is important yet poorly-known, due to low c ulturability and undersampling. However, 16S rRNA gene sequences clone d directly from biomass allow us to know what microbial types are pres ent, irrespective of culturing, and to create probes suitable for biod iversity studies. Many sequences are needed for good probe design. Her e we report on sequences from 57 deep sea clones, obtained by the poly merase chain reaction with 'universal' primers, from 500 m and 3000 m depths in the northeast Pacific and 1000 m depth in the subtropical At lantic. The most common group, with 19 of the new sequences (10 Atlant ic), was a recently reported crenarchaeal cluster, Group I. We also fo und 6 sequences in 2 other archaeal groups in the broad methanogen-hal ophile lineage; 2 of these were in a distinct Lineage not previously r eported. The bacterial sequences included 22 dispersed among the alpha and gamma Proteobacteria (8 related to SAR 11), 5 related to a previo usly reported broad group (Group A) of marine clones poorly affiliated with known (cultured and sequenced) major bacterial divisions, 6 in a second group with little affiliation to any previously reported divis ion (we call this Group B), 1 in a third possible major novel group, 2 deeply branched within the 'Green Nonsulfur' lineage, and 1 branching with a soil clone. In contrast to the vast majority of the sequences, a cluster of 5 sequences was very close to a cultured marine proteoba cterium, Alteromonas macleodii. It appeared that 5 of the clones were chimeric, although this label is difficult to apply when sequences are only distantly related to those in the database, as was common. We co nclude that the deep sea contains numerous novel and widespread major prokaryotic Lineages. Given the huge volume of this habitat and typica l bacterial abundances, it appears that the previously unknown archaea l and bacterial groups may be the most abundant organisms on Earth.