Title:
Controls on nitrogen fixation and nitrogen release in a diazotrophic endosymbiont of shipworms

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dc.contributor.advisor Montoya, Joseph P.
dc.contributor.author Horak, Rachel Elizabeth Ann en_US
dc.contributor.committeeMember DiChristina, Thomas
dc.contributor.committeeMember Hammer, Brian
dc.contributor.committeeMember Joye, Samantha
dc.contributor.committeeMember Kubanek, Julia
dc.contributor.department Biology en_US
dc.date.accessioned 2011-03-04T21:00:00Z
dc.date.available 2011-03-04T21:00:00Z
dc.date.issued 2010-11-15 en_US
dc.description.abstract Nitrogen fixation is an ecologically important microbial process that can contribute bioavailable combined N to habitats low in N. Shipworms, or wood-boring bivalves, host N2-fixing and cellulolytic symbiotic bacteria in gill bacteriocytes, which have been implicated as a necessary adaptation to an N-poor C-rich (wooden) diet. Shipworm symbionts are known to fix N within the gill habitat and newly fixed N is subsequently incorporated into non-symbiont containing host tissue. The presence of N2-fixation in gill bacteriocytes presents a conundrum because N2-fixation is tightly regulated by oxygen in most other diazotrophic microbes. Also, the direct evidence of new N being incorporated into the host tissue indicates that there are potentially complex nutrient cycles in this symbiosis, which have not been investigated. We used the cultivated symbiont Teredinibacter turnerae, which has been isolated from many shipworm species, as a model organism to elucidate controls on N2-fixation and N release in the shipworm symbiosis. Our results indicate that headspace oxygen concentration does not control biomass specific N2-fixation and respiration activity in T. turnerae, but it does influence the magnitude of the growth rate and timing of culture growth. Also, we examined the controls of oxygen on inorganic nutrient uptake rates, and documented a small amount of dissolved inorganic nitrogen release. While the N budget is only partially balanced, we provide indirect evidence for the allocation of fixed N to the excretion of exopolymeric substances and dissolved organic nitrogen; future studies that measure these additional N sinks are necessary to close the N budget. Although there are limitations of using pure cultures to investigate a complex symbiotic system, this study provides direct experimental evidence that T. turnerae has adaptations that are conducive to N2-fixation in gill bacteriocytes. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/37238
dc.publisher Georgia Institute of Technology en_US
dc.subject Endosymbiont en_US
dc.subject Nitrogen release en_US
dc.subject Nitrogen fixation en_US
dc.subject Symbiosis en_US
dc.subject Teredinibacter turnerae en_US
dc.subject Cellulolysis en_US
dc.subject Diazotroph en_US
dc.subject Marine nitrogen cycle en_US
dc.subject.lcsh Nitrogen Fixation
dc.subject.lcsh Shipworms
dc.title Controls on nitrogen fixation and nitrogen release in a diazotrophic endosymbiont of shipworms en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Montoya, Joseph P.
local.contributor.corporatename College of Sciences
local.contributor.corporatename School of Biological Sciences
relation.isAdvisorOfPublication 0000b67d-bef5-4edf-b2d6-3577c297f4c3
relation.isOrgUnitOfPublication 85042be6-2d68-4e07-b384-e1f908fae48a
relation.isOrgUnitOfPublication c8b3bd08-9989-40d3-afe3-e0ad8d5c72b5
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