Algal Research Group

The research in this project has been performed mainly on a unicellular, N2-fixing cyanobacterium of the genus Cyanothece. We have identified several ways in which cyanobacteria can be used to contribute to the sustainability of a space-deployed, bioregenerative life-support system: as a CO2/O2 gas exchange system, as a source of bioavailable nitrogen, as a dietary supplement, and as a contingency in case of catastrophic failure of the plant growth system. Cyanothece may be important in modulating atmospheric CO2 and O2 levels during normal diurnal fluctuations or changes due to crop harvest, since the cyanobacterial gas exchange parameters are plastic and easily manipulated. Although there are no plans to include denitrifying bacterium in the ecosystem, normal plant metabolism or unwanted bacterial blooms could result in large-scale denitrification that would require replenishment of the bioavailable nitrogen supply by fixation of atmospheric nitrogen. Cyanothece may also be used as a source of single cell protein to supplement a vegetarian diet. Finally, if there were to be catastrophic crop failure, Cyanothece could be used to remove atmospheric CO2 and as a source of food and oxygen, thus providing all crew needs in an emergency.

Experiments are being performed in five interrelated areas that are aimed at generating immediate or long-range objectives. The immediate goals include: 1) quantitative aspects of growth, N2 fixation, and gas exchange; 2) determining the potential of cyanobacteria as a dietary supplement; and 3) the impact of environmental stress on biomass production. Longer range objectives include: 4) the analysis of the carbohydrate storage granules that form in cyanobacteria during photosynthesis and are utilized during N2 fixation; and 5) analyzing the periodicity in N2 fixation and O2 evolution in Cyanothece.

Our work will provide a better understanding of photosynthetic productivity under different environmental growth conditions. The analysis of the periodicity in N2 fixation and O2 evolution may provide an interesting model system for the analysis of circadian rhythms in other organisms, including humans. Our preliminary work on Cyanothece as a component of the NASA project led to a successful USDA grant application that will allow study of these mechanisms in more detail. Our goal is to study the molecular and physiological basis of the regulation of photosynthesis and N2 fixation in a single cell. Such studies are clearly of importance to agriculture and may be valuable for crop productivity.

Our long-range experiments might help us understand how N2 fixation in cyanobacteria can be used for fertilization of crops, such as rice. Furthermore, N2-fixing cyanobacteria have the potential to provide an inexpensive source of protein in agriculturally impoverished regions. Cyanothece requires little input of materials, can be grown in simple facilities with little personnel requirements and can provide a balanced protein supplement in large quantities. Additional Earth benefits may be in unique natural products. Cyanothece produces an extracellular matrix that appears to be a hydrocolloid, and may aid food processing applications.

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