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Scientists in the United States have genetically modified an alga by inserting a human gene that allows the plant to grow in the dark. This finding could lead the way to growing large quantities of genetically modified (GM) algae commercially as an inexpensive way of producing drugs and dietary supplements.
Like all plants, algae use sunlight as an energy source in photosynthesis (the production of glucose molecules from water and carbon dioxide). The breakdown of glucose is needed to provide the energy that drives chemical reactions in cells. In the June 15, 2001, issue of Science, a team of scientists led by Kirk Apt of Market Biosciences in Columbia, Maryland, reported that it had inserted a human gene into the alga Phaeododactylum tricornutum. With the human gene, the alga can absorb glucose from its environment, which is something that wild algae cannot do. Therefore, in a glucose-rich environment, the algae can thrive in the dark without needing to produce their own glucose by photosynthesis. In humans, the gene codes for a protein that helps to transport the sugar glucose across the membranes of red blood cells. The researchers were surprised that such a big change in the alga’s metabolism could be effected with the addition of just one gene.
The results may help in creating fermentation techniques for the large-scale exploitation of algae as a source of drugs and dietary supplements. At present, certain species of alga are grown outdoors in ponds and harvested for dietary supplements. The ponds often become contaminated with other microorganisms, and in order to get sufficient light, the alga are restricted to the top of the ponds. By growing GM algae in fermentation vats, the alga is not restricted to the upper layers. The researchers estimate that yields from vats would be 10 to 50 times greater at about one-tenth the expense of growing algae in ponds.
In the March 23, 2001, issue of Cell, cell biologists in the United Kingdom reported the discovery of helical protein filaments that act as an internal framework in bacterial cells, like the cytoskeleton (network of fibrous proteins that gives shape to a cell and governs transport within the cell) in eukaryotes (the cells of animals, plants, protists, and fungi). One of the defining features of a eukaryotic cell has, up until now, been its cytoskeleton, which is made up primarily of filaments of the protein actin. Prokaryotic cells (bacteria and cyanobacteria) were considered to be bags of enzymes without an internal structure, just a tough wall shaping the cell and holding it together. Even electron microscopy studies did not reveal any evidence of a cytoskeleton in prokaryotes.
A team led by Jeffrey Errington of the University of Oxford discovered cytoskeletonlike structures in bacterial cells while studying two genes for the proteins MreB and Mbl, which are known to be involved in determining the shape of bacterial cells. The scientists knocked out each of the genes in the rod-shaped Bacillus subtilis. Without MreB, cells became rounded; without Mbl, cells became long and twisted. Errington’s team also used fluorescent tags to reveal either MreB or Mbl in the altered cells. They found that both proteins formed coiling actinlike filaments, suggesting that the proteins have a cytoskeletonlike role in determining the shape of bacterial cells. The results confirm Errington’s suspicion that something as important as a cytoskeleton must have evolved quite early in life, before prokaryotes and eukaryotes evolved into two groups.