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Geobiology of marine magnetotactic bacteria

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dc.contributor.advisor Katrina J. Edwards. en_US Simmons, Sheri Lynn en_US
dc.contributor.other Woods Hole Oceanographic Institution. en_US 2006-11-06T10:27:53Z 2006-11-06T10:27:53Z 2006 en_US 2006 en_US
dc.description Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2006. en_US
dc.description This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. en_US
dc.description Includes bibliographical references. en_US
dc.description.abstract Magnetotactic bacteria (MTB) biomineralize intracellular membrane-bound crystals of magnetite (Fe3O4) or greigite (Fe3S4), and are abundant in the suboxic to anoxic zones of stratified marine environments worldwide. Their population densities (up to 105 cells ml-1) and high intracellular iron content suggest a potentially significant role in iron cycling, but very little is known about their population dynamics and regulation by environmental geochemistry. The MTB community in Salt Pond (Falmouth, MA), a small stratified marine basin, was used as a model system for quantitative community studies. Magnetiteproducing MTB predominate slightly above the oxic-anoxic interface and greigiteproducing MTB predominate in sulfidic waters. A quantitative PCR (QPCR) assay was developed and applied to enumerate four major groups of MTB in Salt Pond: magnetite-producing cocci, barbells, the greigite-producing many-celled magnetotactic prokaryote (MMP), and a greigite-producing rod. The barbells were identified as [delta]-Proteobacteria while the rod was identified as the first MTB in the [gamma]-Proteobacteria. en_US
dc.description.abstract (cont.) The previously thought to be a single species, consists of at least five clades with greater than 5% divergence in their 16s rRNA. Fluorescent in situ hybridization probes showed significant variation in clade abundances across a seasonal cycle in salt marsh productivity. FISH also showed that aggregates consist of genetically identical cells. QPCR data indicated that populations are finely layered around the oxic-anoxic interface: cocci immediately above the dissolved Fe(II) peak, barbells immediately below, the MMP in microsulfidic waters, and the greigite-producing rod in low numbers (100 cells ml-1) below the gradient region. The barbell reached 1-10% of total eubacteria in the late season, and abundances of cocci and barbells appeared to vary inversely. Calculations based on qPCR data suggest that MTB are significant unrecognized contributors to iron flux in stratified environments. Barbells can respond to high oxygen levels by swimming toward geomagneticsouth, the opposite of all previously reported magnetotactic behavior. This behavior is at least partially dependent on environmental oxidation-reduction potential. The co-existence of MTB with opposing polarities in the same redox environment conflicts with current models of the adaptive value of magnetotaxis. en_US
dc.description.statementofresponsibility by Sheri Lynn Simmons. en_US
dc.format.extent 219 p. en_US
dc.format.extent 10775857 bytes
dc.format.extent 10775471 bytes
dc.format.mimetype application/pdf
dc.format.mimetype application/pdf
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.subject Joint Program in Oceanography. en_US
dc.subject Biology. en_US
dc.subject Woods Hole Oceanographic Institution. en_US
dc.title Geobiology of marine magnetotactic bacteria en_US
dc.title.alternative Geobiology of marine MBT en_US
dc.type Thesis en_US Ph.D. en_US
dc.contributor.department Joint Program in Oceanography. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Biology. en_US
dc.contributor.department Woods Hole Oceanographic Institution. en_US
dc.identifier.oclc 71332105 en_US

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