2024-03-29T04:54:54Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/135212020-11-19T07:16:50Zcom_10261_123com_10261_8col_10261_376
00925njm 22002777a 4500
dc
Massana, Ramon
author
Karniol, Baruch
author
Pommier, Thomas
author
Bodaker, Idan
author
Béjà, Oded
author
2008-02-03
The aim of this study was to explore the use of large-scale sequencing to better describe the genome content of naturally occurring, uncultured protists. We constructed a metagenomic fosmid library from a
picoplanktonic assemblage (0.2–3 mm size cells) collected at the Blanes Bay Microbial Observatory (Western Mediterranean). Seven clones contained a small-subunit ribosomal RNA gene (SSU rDNA) affiliating with prasinophytes and uncultured alveolates. One clone (FBB25; 35 kb in size) was completely sequenced and found to be a tandem repeat array (5.5 times) of the rDNA operon, including three rRNA genes (SSU, large-subunit and 5.8S rDNAs) and three spacer regions (internal transcribed spacers 1, 2 and
intergenic spacer). The SSU rDNA of FBB25 affiliated with the marine alveolates group I, cluster 1, and was almost identical to sequences retrieved only in marine surveys from a wide geographic and ecological range. Phylogenetic trees using the different rRNA genes showed FBB25 as an independent branch among the main alveolate groups, but their closest affiliation varied between the SSU tree (dinoflagellates) and the large-subunit and 5.8S trees (perkinsids). The spacer regions of FBB25 were particularly short when compared with other eukaryotes, indicating a possible genome streamlining in this picoeukaryote. Finally, not a single polymorphism was found in the rDNA repeat array, suggesting that the high SSU rDNA variability typically found in molecular surveys derives from organismal and not intragenomic diversity. This first report on the rDNA genomic structure of an uncultured marine alveolate improves their phylogenetic position and helps interpreting data generated during picoeukaryotic molecular surveys
Environmental Microbiology 10(5): 1335-1343 (2008)
1462-2912
http://hdl.handle.net/10261/13521
10.1111/j.1462-2920.2007.01549.x
Metagenomic retrieval of a ribosomal DNA repeat array from an uncultured marine alveolate