Geobacter sulfurreducens possesses type IV pili that are considered to be conductive nanowires and a crucial structural element in biofilm formation, enabling electron transfer to insoluble metal oxides in anaerobic sediments and to graphite anodes in microbial fuel cells. The molecular mechanism by which electrons are transferred through the nanowires to the electron acceptor is not fully understood. Prior to the work described in this thesis, the gene (pilA) encoding the structural pilus subunit had been identified, but little was known about the functional translation start codon, the length of the mature secreted protein, or what renders the pili conductive. Using mass spectrometry, I found that a tyrosine residue (Y32) near the carboxyl terminus of the mature PilA protein is posttranslationally modified by attachment of glycerophosphate. I studied the significance of Y32 for biofilm formation on various surfaces and for growth of G. sulfurreducens with insoluble electron acceptors. A mutant in which Y32 was replaced by phenylalanine lacked the glycerophosphate; biofilm formation on graphite surfaces was severely diminished and current production in microbial fuel cells was initiated only after a long lag phase. Moreover, cells with Y32F mutation in the pilA gene exhibited growth deficiency when Fe(III) oxide was the sole electron acceptor. My data confirm the role of G. sulfurreducens pili in biofilm formation and electron transfer to Fe(III) oxide and identify an amino acid in the PilA protein that is essential for these two processes. I also confirmed the existence of two functional translation start codons for the pilA gene and identified two isoforms (short and long) of the PilA preprotein by series of genetic complementation experiments. The short PilA isoform is found predominantly in an intracellular fraction, and seems to stabilize the long isoform and influence the secretion of several outer surface c-type cytochromes. The long PilA isoform, on the other hand, is required for secretion of PilA to the outer surface of the cell, a process that requires co-expression of pilA and the nine genes on its 3' side. The long isoform is essential for biofilm formation on various surfaces, for optimum current production in microbial fuel cells, and for growth on insoluble Fe(III) oxide. This study provides new insight concerning the function and biogenesis of Geobacter type IV PilA, as well as a foundation for further research that will be conducted on microbial nanowires.

This chapter introduces a project-based learning lesson that integrates science, English language arts (ELA), and math through a study related to energy sources. Throughout the lesson, students are engaged in a real-world problem of determining the impact of a population on energy resources and discovering ways to build greener, more energy-efficient schools for students of the future. Within this chapter, the authors present a proposed project timeline that teachers can use for implementation within their own classrooms, including an entry event to engage students in the mission of the project. A connection between science, ELA, and math practices is addressed in order to provide students with an opportunity to understand the correlation between all three subject areas. Suggested teaching and learning tasks focused on the driving question of the project and related to all three subject areas are presented along with suggestions for a culminating product and assessment of student learning.

The work presented here investigated two methods of improving productivity in microalgal photobioreactors: applying temperature cycles intended to maximize photosynthesis and minimize respiration, and development of a mathematical model that predicts improvements in photon utilization using temporal light dilution (flashing). The experiments conducted on diurnal temperature cycles with Dunaliella tertiolecta in 30-L outdoor photobioreactors showed that a properly chosen temperature cycle can improve mass and energy productivity by 18% over an identical photobioreactor with a constant temperature. However, excessively large temperature cycle amplitudes reduced productivity. A 4-7% increase in energy content was observed in microalgae exposed to temperature cycles. The physiological reason for this could not be established. A relationship similar to the Bush Equation was obtained that related photon utilization efficiency to flashing frequency, load factor, Photosystem II (PSII) concentration and reaction frequency, and chlorophyll content. The model was validated by the experimental data of a number of researchers.

No description available.

No description available.

No description available.

No description available.

No description available.

Planting woody biomass for energy production can be used as a mine reclamation procedure to satisfy the Surface Mining Control and Reclamation Act of 1977 (SMCRA) and provide renewable energy for the United States.  This study examines the economic viability of bioenergy production on previously mined lands using multiple hardwood species and treatments.  Five species were planted at two densities; one-half of the trees were fertilized in year two.  Height and diameter of the trees were measured annually for five years; the first three years by cooperating researchers at Virginia Tech, the last two years specifically for this report.  Current and predicted mass of the species, effects of planting density and fertilizer application, and the land expectation value (LEV) of each treatment were summarized.  A sensitivity analysis was conducted to determine how changes in production costs, stumpage price, rotation length, and interest rate affect the economic feasibility of bioenergy production.  Renewable energy and mine reclamation policies were investigated and it was determined that woody bioenergy can be planted as a mine reclamation procedure and may receive financial incentives.  Production cost appears to have the largest impact on LEV and is often the difference between positive and negative returns for the landowner.  The extra cost of fertilization and high density planting do not increase LEV; the unfertilized, low density treatments have the best LEV in all examined scenarios.  In general, bioenergy was found to be economically viable as a mine reclamation procedure only in limited circumstances.  In low cost, high price scenarios, bioenergy crops could have the potential to reforest both active and abandoned mine lands throughout southern Appalachia. / Master of Science

Our American electric system doggedly follows the central station model developed in the late 1800s. Thomas Hughes says the system gained momentum by adding more alliances with educators, politicians, and other industries until the social network was so intertwined with the technology that deviating from the central station model would be extremely difficult. However, change can occur if a variety of components change, but Hughes does not specify which components. Another network model, actor-network theory, proposes that social relationships (the same ones that maintain system momentum) are actually dynamic relationships that either actively maintain or change the system configuration. But which relationships need to change in order for utilities to accept and interconnect renewable energy with their grid? This thesis focuses on the social relationships created around renewable technologies and the idea that they can be successfully integrated into the network. In each case, customers, utility executives, institutions, and technology worked together to bring about utility acceptance. Individuals, working within these institutions, can bring about change. In New York City, an urban windmill was installed atop an apartment building. In Sacramento, CA, the municipal utility, SMUD, broke from the system model to become a leader in energy efficiency and renewable energy programs. In Texas, their renewables portfolio standard has become a standard for others to follow. / Master of Science