In addition to wild type forms of Rhodopseudomonas palustris, scientists have used genetically modified forms to produce hydrogen as well. Other explorations include expanding the bioreactor system to hold a combination of bacteria, algae or cyanobacteria. Ethanol production is performed by the algae Chlamydomonas reinhardtii, among other species, in cycling light and dark environments. The cycling of light and dark environments has also been explored with bacteria for hydrogen production, increasing hydrogen yield.