To contribute to the understanding or deep-sea planktonic communities, we e
xplored the prokaryotic diversity. of a 3000 m deep site at the Antarctic P
olar Front using molecular methods. Bacterial 16S rDNA-amplified sequences
corresponded to the as yet uncultivated groups SAR11, within the alpha -Pro
teobacteria, and SAR324. within the delta -Proteobacteria, as well as to th
e gamma -Proteobacteria, Cytophagales. Planctomyces, Gram-positives, and th
e group of environmental sequences SAR406. Among them, gamma -proteobacteri
al sequences were the most abundant and diverse. Within Archaea, and using
six different primer sets for 16S rDNA amplification, only euryarchaeotal s
equences were retrieved. Most of them clustered with the Thermoplasma-relat
ed marine groups II and III, but some corresponded to a recently described
group of marine sequences emerging at the base of haloarchaea. Our data sug
gest that gamma -Proteobacteria and Euryarchaeota may be dominant elements
in terms of genetic diversity of the two prokaryotic domains in this deep-s
ea pelagic area. (C) 2001 Federation of European Microbiological Societies.
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