Carbon, Oxide, Metal Sequestration Mechanisms of Hot Springs Microbial Communities: Establishing a Technical Platform for Chemical Imaging Investigation
EMSL Project ID
48768
Abstract
Though microbes can indirectly and metabolically transform, sequester, and transport (i) ions, (ii) organic and inorganic complexes, and (iii) precipitates via a wide range of mechanisms, implementation challenges remain as to how these attributes can be used in subsurface bioremediation strategies and in recognizing signs of live in the geological record. Until we have a fundamental understanding of the composition of subsurface communities and their intrinsic capabilities to interact with and alter their environment, and acquire the tools and methodologies required to monitor how subsurface processes affect the fate of toxic metals and contaminants, the practice of subsurface bioremediation and understanding of carbon sequestration in mineralizing systems will continue to be an empirical one (Leeson et al., 2005). An alternate approach to expanding current bioremediation/carbon sequestration strategies involves actualistic studies of natural samples collected from environments considered analogs for subsurface regimes. Such analog mineralizing environments, like hot springs, can be accessed routinely to facilitate ongoing investigations of the mechanisms by which extremophile biofilm communities mobilize or sequester carbon, contaminants and toxic elements (e.g., heavy metals) from indigenous hydrothermal fluids. Some of the closest modern relatives of Earth’s most ancient ancestors, which lived in heavy metal-rich hydrothermal regimes, occupy the highest temperature regions of active hot springs (Stetter, 2006). Such studies could pave the way for more sophisticated efforts to identify and harness proteins involved in sequestering toxic elements. A fundamental aspect of such an approach is the ability to document microbe-mineral interactions over time and in natural settings during field and laboratory-based experiments. EMSL scientists are at the forefront of efforts to elucidate how key bacterial soil populations interact with their environment in the critical zone of Earth’s regolith.This proposal seeks to advance an understanding of the processes that lead to carbon sequestration (and novel oxides and metals) associated with remains of organisms. The application of various chemical imaging techniques developed at EMSL that are suited to the interrogation of geomicrobial specimens will be essential for the success of this project. For samples from modern mats, cryoEM specimen preparation and imaging and analysis techniques optimized at EMSL by Dohnalkova et al. will enable the direct study of ultrastructural, intracellular, and extracellular sites where inorganic and organic complexes, minerals, and mineraloids accumulate in association with microbial biofilm communities. Biofilms consist of benthic communities encased in extracellular polymeric substances (EPS) they exude, which, due to the high absorptive capacity of EPS, can sequester organic and inorganic constituents from the environment and facilitate a range of microbe-mineral interactions (e.g., Decho et al., 2005). It has been recognized for some time that the EPS of thermophile and hyperthermophile communities play a key role in sequestering mineraloids in mineralizing hot spring deposits, which are often laminated. Recently, we found (with the use of conventional EM specimen preparation techniques) that fibrils in the integral glycocalyx of thermophilic biofilm EPS can serve as a loci for opaline silica accumulation. We have also discovered that thermophilic organisms in iron-depositing hot springs sequester iron-oxides within the periplasmic space of their cells routinely. This inherent capability––in which an organism extracts a metal ion from its environment, sequesters it via precipitation of a metal oxide in its periplasmic space, and remains viable in the environment––may be more widespread than previously recognized. Intra- and extra-cellular mineralization can also led to carbon sequestration in the geological record. Given that hyperthermophilic and thermophilic biofilms were some of the earliest microbial communities to inhabit our planet and that such communities evolved and thrived in heavy metal-rich ecosystems (and new “mineral formers” are still being discovered in subsurface analog environments like hot springs), it is likely that some members of such communities have inherent sequestration capabilities for oxides and metals and other ions that become concentrated at interfaces in their environment, which may have aided in their survival in such environments. The ability to apply chemical imaging techniques and e.g., cryoEM techniques at EMSL-PNNL is timely in this regard.
Project Details
Start Date
2016-02-11
End Date
2016-09-30
Status
Closed
Released Data Link
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