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Applied and Environmental Microbiology, May 2006, p. 3626-3636, Vol. 72, No. 5
0099-2240/06/$08.00+0 doi:10.1128/AEM.72.5.3626-3636.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
and
Thorsten Stoeck1*
Department of Biology, Technische Universität Kaiserslautern, Erwin-Schrödinger Str. 14, D-67663 Kaiserslautern, Germany,1 Department of Statistical Science, Cornell University, Ithaca, New York 148532
Received 2 December 2005/ Accepted 4 February 2006
To resolve the fine-scale architecture of anoxic protistan communities, we conducted a cultivation-independent 18S rRNA survey in the superanoxic Framvaren Fjord in Norway. We generated three clone libraries along the steep O2/H2S gradient, using the multiple-primer approach. Of 1,100 clones analyzed, 753 proved to be high-quality protistan target sequences. These sequences were grouped into 92 phylotypes, which displayed high protistan diversity in the fjord (17 major eukaryotic phyla). Only a few were closely related to known taxa. Several sequences were dissimilar to all previously described sequences and occupied a basal position in the inferred phylogenies, suggesting that the sequences recovered were derived from novel, deeply divergent eukaryotes. We detected sequence clades with evolutionary importance (for example, clades in the euglenozoa) and clades that seem to be specifically adapted to anoxic environments, challenging the hypothesis that the global dispersal of protists is uniform. Moreover, with the detection of clones affiliated with jakobid flagellates, we present evidence that primitive descendants of early eukaryotes are present in this anoxic environment. To estimate sample coverage and phylotype richness, we used parametric and nonparametric statistical methods. The results show that although our data set is one of the largest published inventories, our sample missed a substantial proportion of the protistan diversity. Nevertheless, statistical and phylogenetic analyses of the three libraries revealed the fine-scale architecture of anoxic protistan communities, which may exhibit adaptation to different environmental conditions along the O2/H2S gradient.
Supplemental material for this article may be found at http://aem.asm.org/.
Present address: Hopkins Marine Station, Department of Biological Sciences, Stanford University, Stanford, CA 93950.
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