For the first time, scientists have introduced a fundamental metabolic change in a single-celled alga so that it no longer requires light to grow.
Photosynthetic algae are the major primary producers in aquatic environments. They are also used in industry for food, to make pigments and cosmetics, and for other applications.
Until now, these organisms have mostly been grown in open ponds where the variability of the environment, light limitation and contamination with microbes are frequent problems.
Scientists have now found that by inserting just one gene that catalyzes glucose transport into the diatom Phaeodactylum tricornutum, the organism can thrive in the dark, getting its energy exclusively from the glucose.
This marks a critical first step toward large-scale, high-density, cost effective cultivation of algae using fermentation technology. The results of this study are published in today's issue of Science.
The Science study is a result of a collaborative effort between researchers at the Department of Plant Biology of the Carnegie Institution of Washington in Palo Alto, California, and Martek Biosciences Corporation in Columbia, Maryland.
Glucose is a primary energy source for most cells. For their experiments, the scientists individually inserted several genes responsible for glucose transport from three different organisms into the diatom Phaeodactylum tricornutum.
One of the genes, Hup1, is from the green alga Chlorella kessleri. Three other genes, Hxt1, Hxt2 and Hxt4, come from the yeast Saccharomyces cervisiae, which is widely used in the brewing and baking industries. The final gene, Glut1, and the one that has shown the most promise, is involved in transporting glucose into human red blood cells to maintain metabolic processes.
The investigators introduced each of these genes into the alga and found that both the Hup1 and Glut1 genes allowed it to take up high levels of glucose and thrive in the dark.
In addition to its industrial potential, the newly engineered diatom will allow scientists to make fundamental discoveries about the processes of photosynthesis and other metabolic activities in algae.
The study also has interesting evolutionary implications. As stated by one of the investigators, Arthur Grossman of Carnegie, "This is the first time that a eukaryotic organism has been transformed from a light-dependent to a light-independent growth mode. It is sobering to think that it required one gene to create such a dramatic difference in life-style. This study, and others, are pointing to a future in which metabolic engineering may be an important means for tailoring organisms to meet the demands of an ever-strained global population."
Henry Linsert, Jr., Martek's Chairman and CEO, sees this work as, "a fundamental breakthrough that opens up the commercial development of the vast number of photosynthetic microalgae and the unique compounds they produce."
The Carnegie Institution of Washington has been a pioneering force in basic scientific research since 1902. It is a private nonprofit organization with five research departments in the U.S.: Terrestrial Magnetism and the Geophysical Laboratory in Washington, D.C., Plant Biology in Stanford, California, Observatories in Pasadena, California, and Embryology in Baltimore, Maryland.
Martek Biosciences Corporation develops, manufactures and sells products from microalgae. The company's products include: (1) specialty nutritional oils for infant formula, nutritional supplements and food ingredients that may play a beneficial role in promoting mental and cardiovascular health, and in the development of the eyes and central nervous system in newborns, (2) high value reagents and technologies to visualize molecular interactions for drug discovery and development, and (3) new, powerful fluorescent markers for diagnostics, rapid miniaturized screening and gene and protein detection.
Carnegie Institution of Washington
Martek Biosciences Corporation
[Contact: Arthur Grossman, Kirk Apt, Tina McDowell]