DIVERSITY OF DEEP-SEA HYDROTHERMAL VENT ARCHAEA FROM LOIHI SEAMOUNT, HAWAII

Through an examination of SSU rDNA (genes coding for SSU rRNA), the mo lecular phylogeny of the domain Archaea (e.g. one of the three major l ineages of life) was analyzed from a microbial mat at an active, deep- sea hydrothermal vent ecosystem located at Pele's Vents on the summit of Loihi Seamount, Hawaii. These SSU rDNAs were amplified from extract ed microbial mat genomic DNA by PCR, cloned into a plasmid vector, and sequenced. The derived archaeal sequences were then used to infer the evolutionary relationships between these microbial mat community memb ers and their closest known relatives. Of the four clones initially ch osen for sequence analysis, a cluster of three phylogenetically simila r PVA (Pele's Vents Archaea) clones all contained in the archaeal grou p I lineage of the marine Crenarchaeota were detected. A single PVA cl one was contained in the archaeal group II lineage of the marine Eurya rchaeota. All four of the PVA clones are novel and constitute the disc overy of new archaeal taxa, From further rarefaction results of 75 arc haeal SSU rDNA clones, we estimate the organismal diversity of this do main from the microbial mats located at Pele's Vents to be significant ly greater than that of the bacterial domain from this same ecosystem, Analyses of archaeal diversity at both the organismal (i.e, rarefacti on) and phylogenetic level suggest that hydrothermal vents, such as Pe le's Vents, are intimately linked with marine archaeoplankton (a recen tly discovered component of marine picoplankton) detected from oceans around the world. (C) 1998 Elsevier Science Ltd. All rights reserved.