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Vol. 152, No.xx , 2006; Pages: 505–517

Metagenomic analysis of mesopelagic Antarctic plankton reveals a novel deltaproteobacterial group

David Moreira,1 Francisco Rodriguez-Valera2 and Purificacion Lopez-Garcia1

1Unite´ d’Ecologie, Systematique et Evolution, CNRS UMR 8079, Universite´ Paris-Sud, 91405
Orsay Cedex, France.


Phylogenetic screening of 3200 clones from a metagenomic library of Antarctic mesopelagic picoplankton allowed the identification of two bacterial 16S-rDNA-containing clones belonging to the Deltaproteobacteria, DeepAnt-1F12 and DeepAnt-32C6. These clones were very divergent, forming a monophyletic cluster with the environmental sequence GR-WP33-58 that branched at the base of the myxobacteria. Except for the possession of complete rrn operons without associated tRNA genes, DeepAnt-1F12 and DeepAnt-32C6 were very different in gene content and organization. Gene density was much higher in DeepAnt-32C6, whereas nearly one-third of DeepAnt-1F12 corresponded to intergenic regions. Many of the predicted genes encoded by these metagenomic clones were informational (i.e. involved in replication, transcription, translation and related processes). Despite this, a few putative cases of horizontal gene transfer were detected, including a transposase. DeepAnt-1F12 contained one putative gene encoding a long cysteine-rich protein, probably membrane-bound and Ca2+-binding, with only eukaryotic homologues. DeepAnt-32C6 carried some predicted genes involved in metabolic pathways that suggested this organism may be anaerobic and able to ferment and to degrade complex compounds extracellularly.

Keywords:Phylogenetic;16S-rDNA;Deltaproteobacteria;deltaproteobacterial;16S rRNA gene;rrn operons;eukaryotic homologues;Bacteria;Archaea;radionuclides.

Corresponding author:

E-mail: puri.lopez@ese.u-psud.fr


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