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Item Nutrient resupplementation arrests bio-oil accumulation in Phaeodactylum tricornutum(2013-08) Valenzuela, Jacob J.; Carlson, Ross P.; Gerlach, Robin; Cooksey, Keith E.; Peyton, Brent M.; Bothner, Brian; Fields, Matthew W.Phaeodactylum tricornutum is a marine diatom in the class Bacillariophyceae and is important ecologically and industrially with regards to ocean primary production and lipid accumulation for biofuel production, respectively. Triacylglyceride (TAG) accumulation has been reported in P. tricornutum under different nutrient stresses, and our results show that lipid accumulation can occur with nitrate or phosphate depletion. However, greater lipid accumulation was observed when both nutrients were depleted as observed using a Nile Red assay and fatty acid methyl ester (FAME) profiles. Nitrate depletion had a greater effect on lipid accumulation than phosphate depletion. Lipid accumulation in P. tricornutum was arrested upon resupplementation with the depleted nutrient. Cells depleted of nitrogen showed a distinct shift from a lipid accumulation mode to cellular growth post resupplementation with nitrate, as observed through increased cell numbers and consumption of accumulated lipid. Phosphate depletion caused lipid accumulation that was arrested upon phosphate resupplementation. The cessation of lipid accumulation was followed by lipid consumption without an increase in cell numbers. Cells depleted in both nitrate and phosphate displayed cell growth upon the addition of both nitrate and phosphate and had the largest observed lipid consumption upon resupplementation. These results indicate that phosphate resupplementation can shut down lipid accumulation but does not cause cells to shift into cellular growth, unlike nitrate resupplementation. These data suggest that nutrient resupplementation will arrest lipid accumulation and that switching between cellular growth and lipid accumulation can be regulated upon the availability of nitrogen and phosphorus.Item Pathways of 2,4,6-trinitrotoluene transformation by aerobic yeasts(2013-08) Ziganshin, Ayrat M.; Gerlach, RobinThe production and use of various highly persistent synthetic compounds lead to environmental pollution. Among such compounds, 2,4,6-trinitrotoluene (TNT) is the one which is commonly used as an explosive. Synthesis and wide use of TNT in ammunition have resulted in the contamination of soil, air, surface water, and groundwater. TNT and its nitro group reduction products are highly toxic, potentially mutagenic and persistent contaminants which can persist in the environment for a long time (Spain et al. 2000; Stenuit et al. 2005; Smets et al. 2007; Singh et al. 2012). The U.S. Environmental Protection Agency has classified TNT as one of the most dangerous pollutants in the biosphere. Hence, remediation of TNT-contaminated sites is urgently warranted at places of its production and use (Keith and Telliard 1979; Fiorella and Spain 1997).Human exposure to TNT or its nitro group reduction metabolites can lead to the development of diseases, such as aplastic anemia, cataracts, impaired liver function and the formation of tumors in the urinary tract (Hathaway 1985; Yinon 1990; Leung et al. 1995). Hence, it is inevitable to work out strategies targeting the degradation of TNT.Decontamination of sites contaminated with explosives, especially with TNT, is possible with application of various physical, chemical, and biological methods. The main advantages of bioremediation are environmental friendliness and involvement of low cost (Rodgers and Bunce 2001).Item Direct measurement and characterization of active photosynthesis zones inside wastewater remediating and biofuel producing microalgal biofilms(2014-03) Bernstein, Hans C.; Kessano, M.; Moll, Karen M.; Smith, Terrence; Gerlach, Robin; Carlson, Ross P.; Miller, Charles D.; Peyton, Brent M.; Cooksey, Keith E.; Gardner, Robert D.; Sims, R. C.Microalgal biofilm based technologies are of keen interest due to their high biomass concentrations and ability to utilize light and CO2. While photoautotrophic biofilms have long been used for wastewater remediation, biofuel production represents a relatively new and under-represented focus area. However, the direct measurement and characterization of fundamental parameters required for industrial control are challenging due to biofilm heterogeneity. This study evaluated oxygenic photosynthesis and respiration on two distinct microalgal biofilms cultured using a novel rotating algal biofilm reactor operated at field- and laboratory-scales. Clear differences in oxygenic photosynthesis and respiration were observed based on different culturing conditions, microalgal composition, light intensity and nitrogen availability. The cultures were also evaluated as potential biofuel synthesis strategies. Nitrogen depletion was not found to have the same effect on lipid accumulation compared to traditional planktonic microalgal studies. Physiological characterizations of these microalgal biofilms identify fundamental parameters needed to understand and control process optimization.Item Struvite stone formation by ureolytic biofilm infections(2016) Schultz, Logan N.; Connolly, James M.; Lauchnor, Ellen G.; Hobbs, Trace; Gerlach, RobinThis chapter describes how urinary tract infections can lead to stone formation. The most frequent type of infection stone is struvite (MgNH4PO4 · 6H2O), although it is common that struvite stones and infections are associated with other stone types, often forming large staghorn calculi. A complete understanding of struvite stone formation requires knowledge of the pathogen biology, including metabolic activity and motility, as well as a basic understanding of how minerals form.The pathogens responsible for struvite stones are those that break down urea into ammonium (NH4 +) and inorganic carbon. This reaction, known as ureolysis, increases the pH of urine and the concentration of NH4 +, thus increasing the saturation index of struvite. If supersaturation is reached, i.e. the ion activity product (IAP) is greater than the ion activity product at equilibrium (Ksp), struvite stone formation is possible.An important consideration with urinary tract infections is that pathogens often form attached communities, known as biofilms, which help them to survive physical and chemical stresses. Not only are biofilm-related infections more difficult to treat, but they can facilitate stone formation by creating gradients in chemical concentrations near surfaces. Modern laboratory bioreactors and computer models, described in this chapter, are improving our understanding of how and why infection stones such as struvite form. Current treatment options for infection stones can be painful or ineffective. As more is learned about the complex microbe-fluid-mineral interactions, less-invasive treatments and more-effective prevention strategies will be developed.Book title: The Role of Bacteria in Urology Lange D, Chew B, (Eds.): Springer, 2015; pp. 41–49.