Metagenomic analysis of mesopelagic Antarctic plankton reveals a novel deltaproteobacterial group.
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.
Moreira
David
D
Unité d'Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud, 91405 Orsay Cedex, France.
Rodríguez-Valera
Francisco
F
División de Microbiología and Evolutionary Genomics Group, Universidad Miguel Hernández, Campus de San Juan, 03550 San Juan de Alicante, Spain.
López-García
Purificación
P
Unité d'Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud, 91405 Orsay Cedex, France.
D000864:Antarctic Regions; D004269:DNA, Bacterial / Q000032:analysis; D004275:DNA, Ribosomal / Q000032:analysis; D020564:Deltaproteobacteria / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D010933:Plankton; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S