The purpose, or objective, of this experiment is to determine the effect of space flight on the morphogenesis and polarity of the one-celled green alga Pleurochrysis carterae, the deposition of calcium into the scales on the cell’s surface, and the relationship of shape and calcification to gravitaxis. Additionally, studies of the relationship between gravity, growth and form, secretion, cell polarity, calcium metabolism and extracellular matrices, cell growth, and reproduction will be conducted.
Bone formed in space does not mineralize properly, and already mineralized bone loses its mineral. The process is difficult to study in vivo, due to systemic effects associated with weightlessness. In vitro systems (cell and organ cultures) have been developed to study mineralization, but are subject to their own problems involving changes in diffusion in space and/or tissue complexity. The calcifying unicellular green algae Pleurochrysis carterae has, instead of a cell wall, a layer of calcified scales called coccoliths. The coccoliths are composed of calcium carbonate (CaCO3) in the form of calcite crystals. Coccoliths are produced in the Golgi cisternae in a precise and orderly manner prior to positioning outside the cell membrane, providing an excellent system for the study of matrix directed calcification without the interference of systemic effects. By studying these algal cells, Dr. Duke and her colleagues can test the theory that the algal cells swim up due to a passive mechanism of orientation. These cells may be of some future use, such as helping in dentistry and removing CO2 from the shuttle/space station environment. Moreover, because P. carterae contains significant nutrients and vitamins, it may be able to provide a calcium supplement in space. On a lighter note, P. carterae does not have much opposition like animals do, except maybe PeTAlgae.
When this experiment will be flown has not yet been decided. At present, this experiment is a candidate for the multi-user European Modular Cultivation System facility being developed by the European Space Agency for the International Space Station.
The experiment itself is to be conducted on the International Space Station. Preparation of the flight experiment will take place at the Kennedy Space Center using cells grown in the PI's lab in Houston. Controls for the experiment will likely be carried out at Ames Research Center in California, using cells from the same cultures as those used for flight. The cells will ride into space on the shuttle in a middeck locker. After docking with the ISS, the cultures will be transferred to the station and placed in the European Modular Cultivation System (EMCS). After launch, the PI and her lab will return from KSC and ARC, respectively, and monitor the experiment and the ground controls from the School of Dentistry in Houston.
Because this experiment requires live cells to be brought back from space, it will take place at the end of a 90-day increment, or period of time, of which it is a part. For the first 70 days of the increment, the algal cells will be stored in the cold (40oC) and dark. The experiment will be activated by placing the containers with algae cultures in the EMCS where they will be cultured at temperature and light suitable for photosynthesis for about three weeks .