title: Diversity patterns and activity of uncultured marine heterotrophic flagellates unveiled with pyrosequencing.
abstract: Flagellated heterotrophic microeukaryotes have key roles for the functioning of marine ecosystems as they channel large amounts of organic carbon to the upper trophic levels and control the population sizes of bacteria and archaea. Still, we know very little on the diversity patterns of most groups constituting this evolutionary heterogeneous assemblage. Here, we investigate 11 groups of uncultured flagellates known as MArine STramenopiles (MASTs). MASTs are ecologically very important and branch at the base of stramenopiles. We explored the diversity patterns of MASTs using pyrosequencing (18S rDNA) in coastal European waters. We found that MAST groups range from highly to lowly diversified. Pyrosequencing (hereafter '454') allowed us to approach to the limits of taxonomic diversity for all MAST groups, which varied in one order of magnitude (tens to hundreds) in terms of operational taxonomic units (98% similarity). We did not evidence large differences in activity, as indicated by ratios of DNA:RNA-reads. Most groups were strictly planktonic, although we found some groups that were active in sediments and even in anoxic waters. The proportion of reads per size fraction indicated that most groups were composed of very small cells (∼2-5 μm). In addition, phylogenetically different assemblages appeared to be present in different size fractions, depths and geographic zones. Thus, MAST diversity seems to be highly partitioned in spatial scales. Altogether, our results shed light on these ecologically very important but poorly known groups of uncultured marine flagellates.
authors.affiliation: Institut de Ciències del Mar (CSIC), Passeig Marítim de la Barceloneta, Barcelona, Spain. ramiro.logares@gmail.com
authors.forename: Ramiro
authors.initials: R
authors.lastname: Logares
authors.forename: Stephane
authors.initials: S
authors.lastname: Audic
authors.forename: Sebastien
authors.initials: S
authors.lastname: Santini
authors.forename: Massimo C
authors.initials: MC
authors.lastname: Pernice
authors.forename: Colomban
authors.initials: C
authors.lastname: de Vargas
authors.forename: Ramon
authors.initials: R
authors.lastname: Massana
mesh_terms: D044822:Biodiversity; D052836:Heterotrophic Processes; D010802:Phylogeny; D010933:Plankton / Q000145:classification / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D058009:Stramenopiles / Q000145:classification* / Q000235:genetics
chemical_list: D012337:RNA, Ribosomal, 18S