期刊
PLOS ONE
卷 6, 期 3, 页码 -出版社
PUBLIC LIBRARY SCIENCE
DOI: 10.1371/journal.pone.0017769
关键词
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资金
- NSF [IOS 0951077]
- NASA Astrobiology Institute
- Swarthmore College
- NSF MRI [OCE-821374, OCE-1019242]
- Maine Technology Institute
- NSF SGER [EF-0633142, MCB-738232]
- Direct For Biological Sciences
- Division Of Integrative Organismal Systems [951077] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Ocean Sciences [0755142] Funding Source: National Science Foundation
- Division Of Ocean Sciences
- Directorate For Geosciences [0821374] Funding Source: National Science Foundation
Leptothrix ochracea is a common inhabitant of freshwater iron seeps and iron-rich wetlands. Its defining characteristic is copious production of extracellular sheaths encrusted with iron oxyhydroxides. Surprisingly, over 90% of these sheaths are empty, hence, what appears to be an abundant population of iron-oxidizing bacteria, consists of relatively few cells. Because L. ochracea has proven difficult to cultivate, its identification is based solely on habitat preference and morphology. We utilized cultivation-independent techniques to resolve this long-standing enigma. By selecting the actively growing edge of a Leptothrix-containing iron mat, a conventional SSU rRNA gene clone library was obtained that had 29 clones (42% of the total library) related to the Leptothrix/Sphaerotilus group (<= 96% identical to cultured representatives). A pyrotagged library of the V4 hypervariable region constructed from the bulk mat showed that 7.2% of the total sequences also belonged to the Leptothrix/Sphaerotilus group. Sorting of individual L. ochracea sheaths, followed by whole genome amplification (WGA) and PCR identified a SSU rRNA sequence that clustered closely with the putative Leptothrix clones and pyrotags. Using these data, a fluorescence in-situ hybridization (FISH) probe, Lepto175, was designed that bound to ensheathed cells. Quantitative use of this probe demonstrated that up to 35% of microbial cells in an actively accreting iron mat were L. ochracea. The SSU rRNA gene of L. ochracea shares 96% homology with its closet cultivated relative, L. cholodnii, This establishes that L. ochracea is indeed related to this group of morphologically similar, filamentous, sheathed microorganisms.
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