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Molecular hydrogen is a promising currency in the future energy economy due to the uncertain availability of finite fossil fuel resources and environmental effects from their combustion. It also has important uses in the production of fertilizers and platform chemicals as well as in upgrading conventional fuels. Conventional methods for producing molecular hydrogen from natural gas produce carbon dioxide and use a finite resource as feedstock. However, these issues can be overcome by using light energy from the Sun combined with microorganisms and their molecular machinery capable of photosynthesis. In the presence of light, the proteins involved in photosynthesis coupled with appropriate catalysts in higher plants, algae, and cyanobacteria can produce molecular hydrogen, and optimization via genetic modifications and biomolecular engineering further improves production rates. In this review, we will discuss techniques that have been utilized to improve rates of hydrogen production in biological systems based on the protein machinery of photosynthesis coupled with appropriate catalysts. We will also suggest areas for improvement and future directions for work in the field.

There is considerable interest in making use of solar energy through photosynthesis to create alternative forms of fuel. Here, we show that photosystem I from a thermophilic bacterium and cytochrome- c 6 can, in combination with a platinum catalyst, generate a stable supply of hydrogen in vitro upon illumination. The self-organized platinization of the photosystem I nanoparticles allows electron transport from sodium ascorbate to photosystem I via cytochrome- c 6 and finally to the platinum catalyst, where hydrogen gas is formed. Our system produces hydrogen at temperatures up to 55 °C and is temporally stable for >85 days with no decrease in hydrogen yield when tested intermittently. The maximum yield is ∼ 5.5 µmol H 2 h −1  mg −1 chlorophyll and is estimated to be ∼25-fold greater than current biomass-to-fuel strategies. Future work will further improve this yield by increasing the kinetics of electron transfer, extending the spectral response and replacing the platinum catalyst with a renewable hydrogenase. Photosynthetic nanoparticles obtained from a thermophilic bacterium can produce a stable supply of hydrogen at temperatures up to 55 °C with a yield that is approximately 25 times greater than current hydrogen production strategies.

Knowing how motile bacteria move near and along a solid surface is crucial to understanding such diverse phenomena as the migration of infectious bacteria along a catheter, biofilm growth, and the movement of bacteria through the pore spaces of saturated soil, a critical step in the in situ bioremediation of contaminated aquifers. In this study, a tracking microscope is used to record the three-dimensional motion of Escherichia coli near a planar glass surface. Data from the tracking microscope are analyzed to quantify the effects of bacteria-surface interactions on the swimming behavior of bacteria. The speed of cells approaching the surface is found to decrease in agreement with the mathematical model of Ramia et al. [Ramia, M., Tullock, D. L. \\& Phan-Tien, N. (1993) Biophys J. 65,755-778], which represents the bacteria as spheres with a single polar flagellum rotating at a constant rate. The tendency of cells to swim adjacent to the surface is shown in computer-generated reproductions of cell traces. The attractive interaction potential between the cells and the solid surface is offered as one of several possible explanations for this tendency.

A three-stage system was developed to automate a batchwise toxicity testing protocol designed for assessing wastewater toxicity to activated sludge. The three-stage system used the luminescent bacterium Shk1. The three stages were cell storage, cell activation, and continuous toxicity testing. Shk1 cells were stored in a bioreactor at 4°C when the system was not in use and activated in another bioreactor for use in toxicity tests conducted in a continuous manner. The system could quickly be switched between the \"off\" and \"on\" modes, and operation of the system was easy. The stability of the system, in terms of cell density and bioluminescence in the storage and activation bioreactors, and the response of the activated cells to a metal and an organic toxicant were studied. The feasibility of the system design was demonstrated by simulating zinc toxicity episodes in synthetic wastewater. The needs for further modifications and improvements of the system were discussed.

The reduction rate of photo-oxidized Photosystem I (PSI) with various natural and artificial electron donors have been well studied by transient absorption spectroscopy. The electron transfer rate from various donors to P 700 + has been measured for a wide range of photosynthetic organisms encompassing cyanobacteria, algae, and plants. PSI can be a limiting component due to tedious extraction and purification methods required for this membrane protein. In this report, we have determined the in vivo, intracellular cytochrome c 6 (cyt c 6 )/PSI ratio in Thermosynechococcus elongatus ( T.e. ) using quantitative Western blot analysis. This information permitted the determination of P 700 + reduction kinetics via recombinant cyt c 6 in a physiologically relevant ratio (cyt c 6 : PSI) with a Joliot-type, LED-driven, pump-probe spectrophotometer. Dilute PSI samples were tested under varying cyt c 6 concentration, temperature, pH, and ionic strength, each of which shows similar trends to the reported literature utilizing much higher PSI concentrations with laser-based spectrophotometer. Our results do however indicate kinetic differences between actinic light sources (laser vs. LED), and we have attempted to resolve these effects by varying our LED light intensity and duration. The standardized configuration of this spectrophotometer will also allow a more uniform kinetic analysis of samples in different laboratories. We can conclude that our findings from the LED-based system display an added total protein concentration effect due to multiple turnover events of P 700 + reduction by cyt c 6 during the longer illumination regime.

The reduction rate of photo-oxidized Photosystem I (PSI) with various natural and artificial electron donors have been well studied by transient absorption spectroscopy. The electron transfer rate from various donors to P700 + has been measured for a wide range of photosynthetic organisms encompassing cyanobacteria, algae, and plants. PSI can be a limiting component due to tedious extraction and purification methods required for this membrane protein. In this report, we have determined the in vivo, intracellular cytochrome c 6 (cyt c 6)/PSI ratio in Thermosynechococcus elongatus (T.e.) using quantitative Western blot analysis. This information permitted the determination of P700 + reduction kinetics via recombinant cyt c 6 in a physiologically relevant ratio (cyt c 6: PSI) with a Joliot-type, LED-driven, pump-probe spectrophotometer. Dilute PSI samples were tested under varying cyt c 6 concentration, temperature, pH, and ionic strength, each of which shows similar trends to the reported literature utilizing much higher PSI concentrations with laser-based spectrophotometer. Our results do however indicate kinetic differences between actinic light sources (laser vs. LED), and we have attempted to resolve these effects by varying our LED light intensity and duration. The standardized configuration of this spectrophotometer will also allow a more uniform kinetic analysis of samples in different laboratories. We can conclude that our findings from the LED-based system display an added total protein concentration effect due to multiple turnover events of P700 + reduction by cyt c 6 during the longer illumination regime.

The reduction rate of photo-oxidized Photosystem I (PSI) with various natural and artificial electron donors have been well studied by transient absorption spectroscopy. The electron transfer rate from various donors to P sub(700) super(+) has been measured for a wide range of photosynthetic organisms encompassing cyanobacteria, algae, and plants. PSI can be a limiting component due to tedious extraction and purification methods required for this membrane protein. In this report, we have determined the in vivo, intracellular cytochrome c sub(6) (cyt c sub(6))/PSI ratio in Thermosynechococcus elongatus (T.e.) using quantitative Western blot analysis. This information permitted the determination of P sub(700) super(+) reduction kinetics via recombinant cyt c sub(6) in a physiologically relevant ratio (cyt c sub(6): PSI) with a Joliot-type, LED-driven, pump-probe spectrophotometer. Dilute PSI samples were tested under varying cyt c sub(6) concentration, temperature, pH, and ionic strength, each of which shows similar trends to the reported literature utilizing much higher PSI concentrations with laser-based spectrophotometer. Our results do however indicate kinetic differences between actinic light sources (laser vs. LED), and we have attempted to resolve these effects by varying our LED light intensity and duration. The standardized configuration of this spectrophotometer will also allow a more uniform kinetic analysis of samples in different laboratories. We can conclude that our findings from the LED-based system display an added total protein concentration effect due to multiple turnover events of P sub(700) super(+) reduction by cyt c sub(6) during the longer illumination regime.

The reduction rate of photo-oxidized Photosystem I (PSI) with various natural and artificial electron donors have been well studied by transient absorption spectroscopy. The electron transfer rate from various donors to P700+ has been measured for a wide range of photosynthetic organisms encompassing cyanobacteria, algae, and plants. PSI can be a limiting component due to tedious extraction and purification methods required for this membrane protein. In this report, we have determined the in vivo, intracellular cytochrome c 6 (cyt c 6)/PSI ratio in Thermosynechococcus elongatus (T.e.) using quantitative Western blot analysis. This information permitted the determination of P700+ reduction kinetics via recombinant cyt c 6 in a physiologically relevant ratio (cyt c 6: PSI) with a Joliot-type, LED-driven, pump-probe spectrophotometer. Dilute PSI samples were tested under varying cyt c 6 concentration, temperature, pH, and ionic strength, each of which shows similar trends to the reported literature utilizing much higher PSI concentrations with laser-based spectrophotometer. Our results do however indicate kinetic differences between actinic light sources (laser vs. LED), and we have attempted to resolve these effects by varying our LED light intensity and duration. The standardized configuration of this spectrophotometer will also allow a more uniform kinetic analysis of samples in different laboratories. We can conclude that our findings from the LED-based system display an added total protein concentration effect due to multiple turnover events of P700+ reduction by cyt c 6 during the longer illumination regime.The reduction rate of photo-oxidized Photosystem I (PSI) with various natural and artificial electron donors have been well studied by transient absorption spectroscopy. The electron transfer rate from various donors to P700+ has been measured for a wide range of photosynthetic organisms encompassing cyanobacteria, algae, and plants. PSI can be a limiting component due to tedious extraction and purification methods required for this membrane protein. In this report, we have determined the in vivo, intracellular cytochrome c 6 (cyt c 6)/PSI ratio in Thermosynechococcus elongatus (T.e.) using quantitative Western blot analysis. This information permitted the determination of P700+ reduction kinetics via recombinant cyt c 6 in a physiologically relevant ratio (cyt c 6: PSI) with a Joliot-type, LED-driven, pump-probe spectrophotometer. Dilute PSI samples were tested under varying cyt c 6 concentration, temperature, pH, and ionic strength, each of which shows similar trends to the reported literature utilizing much higher PSI concentrations with laser-based spectrophotometer. Our results do however indicate kinetic differences between actinic light sources (laser vs. LED), and we have attempted to resolve these effects by varying our LED light intensity and duration. The standardized configuration of this spectrophotometer will also allow a more uniform kinetic analysis of samples in different laboratories. We can conclude that our findings from the LED-based system display an added total protein concentration effect due to multiple turnover events of P700+ reduction by cyt c 6 during the longer illumination regime.

Heavy metals are known to be inhibitory and toxic to the activated-sludge microbial community in biological wastewater treatment plants. Toxicity screening of aqueous mixtures of these heavy metal ions in plant influent could use both chemical and biological methods. As a biological method, luminescent bacterial bioreporters offer the advantages of a simple test procedure and rapid response. Current biologically based methods for screening aqueous streams for toxicity are labor-intensive, inaccurate, or difficult to use in continuous monitoring applications. In the present study, a system was developed that is simple and easily automated. This system is based on the bacterium Shk1, a genetically engineered bioluminescent Pseudomonad whose parent strain was originally isolated from activated sludge. Compared with other bioluminescence-based systems (specifically, the Microtox assay), the system of the present study more accurately reflects the effects of the toxicity of common metal ions on activated-sludge respirometry without being overly sensitive to typical constituents of wastewater. The use Shk1 as a bioluminescent reporter for heavy metal toxicity testing for the application of wastewater treatment influent toxicity screening is presented in this study.

The reduction rate of photo-oxidized Photosystem I (PSI) with various natural and artificial electron donors have been well studied by transient absorption spectroscopy. The electron transfer rate from various donors to P.sub.700.sup.+ has been measured for a wide range of photosynthetic organisms encompassing cyanobacteria, algae, and plants. PSI can be a limiting component due to tedious extraction and purification methods required for this membrane protein. In this report, we have determined the in vivo, intracellular cytochrome c.sub.6 (cyt c.sub.6)/PSI ratio in Thermosynechococcus elongatus (T.e.) using quantitative Western blot analysis. This information permitted the determination of P.sub.700.sup.+ reduction kinetics via recombinant cyt c.sub.6 in a physiologically relevant ratio (cyt c.sub.6: PSI) with a Joliot-type, LED-driven, pump-probe spectrophotometer. Dilute PSI samples were tested under varying cyt c.sub.6 concentration, temperature, pH, and ionic strength, each of which shows similar trends to the reported literature utilizing much higher PSI concentrations with laser-based spectrophotometer. Our results do however indicate kinetic differences between actinic light sources (laser vs. LED), and we have attempted to resolve these effects by varying our LED light intensity and duration. The standardized configuration of this spectrophotometer will also allow a more uniform kinetic analysis of samples in different laboratories. We can conclude that our findings from the LED-based system display an added total protein concentration effect due to multiple turnover events of P.sub.700.sup.+ reduction by cyt c.sub.6 during the longer illumination regime.