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Microbial Colonization of Minerals in Marine Sediments – Method Development and Ecological Significance


Harrison, Benjamin Kimball (2011) Microbial Colonization of Minerals in Marine Sediments – Method Development and Ecological Significance. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/3891-QQ56.


Interactions between microorganisms and minerals significantly impact microbial diversity and geochemical cycles in diverse settings. However, methodological difficulty has inhibited past study of microbe–mineral interactions in fine-grained subsurface environments. Conventional sampling poorly resolves microbial diversity at the fine scale necessary to perceive overall community differences between mineral substrates that are thoroughly mixed. In particular, the importance of microbial attachment to minerals in unconsolidated marine sediments remains poorly constrained despite extensive geobiological research in these settings. This study presents an approach for characterizing microbial colonization patterns using mineral separation techniques. Differences in density and magnetic susceptibility are used to enrich target minerals from bulk environmental samples, selecting for those minerals which may have importance as substrates for metabolic activity.

The application of this methodology to methane seep sediments of the Eel River Basin (ERB) on the California margin demonstrates that variations in microbial diversity between minerals are comparable to community differences across broad spatial scales and a range of porewater geochemistry. ERB colonization patterns determined by separation are shown to be reproducible and reflect in situ differences in the microbial community. Affinity of putative sulfide-oxidizing bacteria (primarily identified as Gammaproteobacteria) for mineral partitions enriched in authigenic sulfides suggests microbial attachment may reflect a metabolic role in sulfur cycling under reducing conditions. Mineral attachment is also shown to select between key archaeal phylotypes involved in the anaerobic oxidation of methane (AOM), providing insight into physiological differences between these uncultured groups. Preliminary results demonstrate that mineral attachment may be a significant factor in the microbial diversity of the marine subsurface, and that such community differences will be ecologically relevant.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Geochemistry; Environmental Microbiology; Methane Seeps; Mineralogy; Oceanography
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geochemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Orphan, Victoria J.
Thesis Committee:
  • Eiler, John M. (chair)
  • Rossman, George Robert
  • Adkins, Jess F.
  • Orphan, Victoria J.
  • Edwards, Katrina J.
Defense Date:5 May 2011
Non-Caltech Author Email:bkimballh (AT)
Record Number:CaltechTHESIS:05262011-085126961
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6448
Deposited By: Benjamin Harrison
Deposited On:31 May 2011 18:28
Last Modified:09 Oct 2019 17:10

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