Sat, 26 Jul 2008 06:36:06 BST CiteULike: vrich crens http://www.citeulike.org/user/vrich/tag/crens CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/vrich/article/1672724 <i>Environmental Microbiology, Vol. 6, No. 1. (2004), pp. 19-34.</i><br /><br />Summary Marine planktonic crenarchaeota have escaped all cultivation attempts to date, all crenarchaeota growing in pure culture so far being hyperthermophiles. Here, we present a comparative genomic analysis of a 16S- plus 23S-rDNA-containing fragment of a crenarchaeote retrieved from an environmental genomic library constructed from picoplankton collected at 500 m depth in the Antarctic Polar Front. The clone DeepAnt-EC39 contained an insert of 33.3 kbp, which was completely sequenced. DeepAnt-EC39 appears to represent a lineage specific to deep-sea waters but widespread geographically, as revealed by the analysis of the 16S-23S-rDNA intergenic spacer region. A comparison with previously sequenced marine crenarchaeotal genomic clones also containing an rrn operon (74A4, 4B7 and Cenarchaeum symbiosum strains A and B) revealed a highly variable structure involving gene rearrangements and insertions/deletions. The surroundings of the rrn operon and the contiguous glutamate-1-semialdehyde aminotransferase gene appear hot spots for recombination. Phylogenetic analyses of all individual predicted proteins revealed the existence of several likely cases of horizontal gene transfer both, between the two archaeal kingdoms and between the two prokaryotic domains. The most frequent horizontal transfers appear to involve genes from mesophilic methanogenic euryarchaeota related to Methanosarcinales. We hypothesise that the acquisition of genes from mesophilic bacteria and euryarchaeota has played a major role in the adaptation of Group I crenarchaeota to life at lower temperatures. Comparative analysis of a genome fragment of an uncultivated mesopelagic crenarchaeote reveals multiple horizontal gene transfers Purificacion Lopez-Garcia Celine Brochier David Moreira Francisco Rodriguez-Valera doi:10.1046/j.1462-2920.2003.00533.x Environmental Microbiology, Vol. 6, No. 1. (2004), pp. 19-34. 2007-09-19T01:24:21-00:00 2004 Environmental Microbiology 6 1 19 34 antarctic archaea crens deep_ant hgt http://www.citeulike.org/user/vrich/article/937612 <i>Appl Environ Microbiol, Vol. 63, No. 1. (January 1997), pp. 50-56.</i><br /><br />Newly described phylogenetic lineages within the domain Archaea have recently been found to be significant components of marine picoplankton assemblages. To better understand the ecology of these microorganisms, we investigated the relative abundance, distribution, and phylogenetic composition of Archaea in the Santa Barbara Channel. Significant amounts of archaeal rRNA and rDNA (genes coding for rRNA) were detected in all samples analyzed. The relative abundance of archaeal rRNA as measured by quantitative oligonucleotide hybridization experiments was low in surface waters but reached higher values (20 to 30% of prokaryotic rRNA) at depths below 100 m. Probes were developed for the two major groups of marine Archaea detected. rRNA originating from the euryarchaeal group (group II) was most abundant in surface waters, whereas rRNA from the crenarchaeal group (group I) dominated at depth. Clone libraries of PCR-amplified archaeal rRNA genes were constructed with samples from 0 and 200 m deep. Screening of libraries by hybridization with specific oligonucleotide probes, as well as subsequent sequencing of the cloned genes, indicated that virtually all archaeal rDNA clones recovered belonged to one of the two groups. The recovery of cloned rDNA sequence types in depth profiles exhibited the same trends as were observed in quantitative rRNA hybridization experiments. One representative of each of 18 distinct restriction fragment length polymorphism types was partially sequenced. Recovered sequences spanned most of the previously reported phylogenetic diversity detected in planktonic crenarchaeal and euryarchaeal groups. Several rDNA sequences appeared to be harbored in archaeal types which are widely distributed in marine coastal waters. In total, data suggest that marine planktonic crenarchaea and euryarchaea of temperate coastal habitats thrive in different zones of the water column. The relative rRNA abundance of the crenarchaeal group suggests that its members constitute a significant fraction of the prokaryotic biomass in subsurface coastal waters. Vertical distribution and phylogenetic characterization of marine planktonic Archaea in the Santa Barbara Channel. R Massana AE Murray CM Preston EF DeLong Appl Environ Microbiol, Vol. 63, No. 1. (January 1997), pp. 50-56. 2006-11-09T12:08:58-00:00 1997 Appl Environ Microbiol 0099-2240 63 1 50 56 archaea crens eurys santa_barbara_chanel http://www.citeulike.org/user/vrich/article/2750707 <i>Nature, Vol. 409, No. 6819. (25 January 2001), pp. 507-510.</i> Archaeal dominance in the mesopelagic zone of the Pacific Ocean Markus Karner Edward Delong David Karl doi:10.1038/35054051 Nature, Vol. 409, No. 6819. (25 January 2001), pp. 507-510. 2008-05-03T21:10:36-00:00 2001 Nature 409 6819 507 510 archaea crens fish gi