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Related stuff, as a reprise. Links are probably dead, check the Web Archive.

Chlamydomonas reinhardtii that has been genetically modified can produce hydrogen as a byproduct of photosynthesis.

Patent filed on energy discovery
by Kathleen Scalise
A metabolic switch that triggers algae to turn sunlight into large quantities of hydrogen gas, a valuable fuel, is the subject of a new discovery reported for the first time by University of California, Berkeley, scientists and their Colorado colleagues. UC Berkeley plant and microbial biology professor Tasios Melis and postdoctoral associate Liping Zhang of UC Berkeley made the discovery -- funded by the U.S. Department of Energy (DOE) Hydrogen Program -- with Dr. Michael Seibert, Dr. Maria Ghirardi and postdoctoral associate Marc Forestier of the National Renewable Energy Laboratory (NREL) in Golden, Colorado. Currently, hydrogen fuel is extracted from natural gas, a non-renewable energy source. The new discovery makes it possible to harness nature's own tool, photosynthesis, to produce the promising alternative fuel from sunlight and water. A joint patent on this new technique for capturing solar energy has been taken out by the two institutions. While current production rates are not high enough to make the process immediately viable commercially, the researchers believe that yields could rise by at least 10 fold with further research, someday making the technique an attractive fuel-producing option. Preliminary rough estimates, for instance, suggest it is conceivable that a single, small commercial pond could produce enough hydrogen gas to meet the weekly fuel needs of a dozen or so automobiles, Melis said.
Abstract Number:1027
by Maria L Ghirardi and Michael Seibert
The hydrogen metabolism of photosynthetic bacteria and cyanobacteria involves the coordinated action of three enzymes: nitrogenase, reversible hydrogenase, and uptake hydrogenase. Green algae, on the other hand, contain only the reversible hydrogenase, which is responsible for both hydrogen production and uptake in this organism. The quantum yield for hydrogenase-catalyzed hydrogen production is much higher than that for nitrogenase. Algal hydrogenases, however, are extremely sensitive to oxygen. For this reason, green algae cannot be utilized commercially for hydrogen production. We have investigated two types of selective pressure to isolate mutants of Chlamydomonas reinhardtii that produce hydrogen in the presence of oxygen. The first is based on competition between hydrogenase and metronidazole for electrons from light-reduced ferredoxin. Since reduction of metronidazole results in the release of toxic products that eventually kill the organism, cells with an active oxygen-tolerant hydrogenase will survive a short treatment with the drug in the light in the presence of oxygen. Using this technique, we have isolated a variant of C. reinhardtii that evolves hydrogen with an I50 for oxygen three times higher than the wild type strain. The second selective pressure depends on growth of algal cells under photoreductive conditions. Algal cells must fix carbon dioxide in the presence of oxygen with reductants derived from hydrogen uptake by the reversible hydrogenase. We will describe in detail both selective pressures, as well as the characteristics of the mutants isolated by application of these selective pressures to a population of mutagenized wild type cells. This work was supported by the U.S. DOE Hydrogen Program.
The Department of Energy's Biohydrogen Research Program
by Maria L Ghirardi and Michael Seibert
A recent discovery at ORNL demonstrated that hydrogen production from a green algal Chlamydomonas reinhardtii mutant cannot easily be explained by the Z-scheme, the standard model of photosynthesis. Too much hydrogen was produced to be accounted for by this model. These results may have implications for designing a commercial BioHydrogen organism with improved energetic conversion efficiencies of hydrogen production, especially in the context of the light saturation problem.
Plankton Power
New Scientist
Tiny marine plants and animals can provide limitless power for small electric devices. Plankton in seawater and sediment use different chemical reactions to obtain their energy. This sets up a natural potential difference between the seawater and the sediment a few centimetres beneath. A device called OSCAR (Ocean Sediment Carbon Aerobic Reactor) taps into this tiny voltage. Leonard Tender of the US Naval Research Laboratory believes his system would be ideal for powering oceanographic sensors, whose batteries currently need to be replaced constantly.

All that's needed now is a seawater version of this critter, and we'll have an unnatural plant that can process seawater into hydrogen for fuel, which when burned can provide freshwater. : )