title: Metagenomics of the deep Mediterranean, a warm bathypelagic habitat.
abstract: BACKGROUND
  Metagenomics is emerging as a powerful method to study the function and physiology of the unexplored microbial biosphere, and is causing us to re-evaluate basic precepts of microbial ecology and evolution. Most marine metagenomic analyses have been nearly exclusively devoted to photic waters.
  
  
  RESULTS
  We constructed a metagenomic fosmid library from 3,000 m-deep Mediterranean plankton, which is much warmer (approximately 14 degrees C) than waters of similar depth in open oceans (approximately 2 degrees C). We analyzed the library both by phylogenetic screening based on 16S rRNA gene amplification from clone pools and by sequencing both insert extremities of ca. 5,000 fosmids. Genome recruitment strategies showed that the majority of high scoring pairs corresponded to genomes from Rhizobiales within the Alphaproteobacteria, Cenarchaeum symbiosum, Planctomycetes, Acidobacteria, Chloroflexi and Gammaproteobacteria. We have found a community structure similar to that found in the aphotic zone of the Pacific. However, the similarities were significantly higher to the mesopelagic (500-700 m deep) in the Pacific than to the single 4000 m deep sample studied at this location. Metabolic genes were mostly related to catabolism, transport and degradation of complex organic molecules, in agreement with a prevalent heterotrophic lifestyle for deep-sea microbes. However, we observed a high percentage of genes encoding dehydrogenases and, among them, cox genes, suggesting that aerobic carbon monoxide oxidation may be important in the deep ocean as an additional energy source.
  
  
  CONCLUSIONS
  The comparison of metagenomic libraries from the deep Mediterranean and the Pacific ALOHA water column showed that bathypelagic Mediterranean communities resemble more mesopelagic communities in the Pacific, and suggests that, in the absence of light, temperature is a major stratifying factor in the oceanic water column, overriding pressure at least over 4000 m deep. Several chemolithotrophic metabolic pathways could supplement organic matter degradation in this most depleted habitat.
authors: División de Microbiología, Universidad Miguel Hernández, San Juan de Alicante, Spain.
authors: Ana-Belen
authors: AB
authors: Martín-Cuadrado
authors: Purificación
authors: P
authors: López-García
authors: Juan-Carlos
authors: JC
authors: Alba
authors: David
authors: D
authors: Moreira
authors: Luis
authors: L
authors: Monticelli
authors: Axel
authors: A
authors: Strittmatter
authors: Gerhard
authors: G
authors: Gottschalk
authors: Francisco
authors: F
authors: Rodríguez-Valera
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D023281:Genomics; D008522:Mediterranean Sea; D010802:Phylogeny; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers