Injecting a gene from red blood cells gives microalgae the power to grow in the dark. Normally the microalgae rely on photosynthesis, but once reengineered, they can take up sugar for energy instead. Researchers hope to duplicate the process in other species, possibly opening the door to cheap mass production of algae-derived pharmaceuticals.
Like green plants, microalgae, also called diatoms, survive by converting sunlight into energy by photosynthesis. Corporations that want to mass-produce algae-derived products, such as antioxidants or other dietary supplements, must grow the algae in large outdoor ponds, which are susceptible to contamination and unpredictable weather. A cheaper, more efficient large-scale cultivation technique already exists: microbial fermenters, giant stainless steel tanks such as those used for growing bacteria or yeast. But most microalgae can't grow inside the dark tanks.
The first step toward growing microalgae without light was enabling the cells to take up glucose. A team led by molecular biologist Kirk Apt of Martek Biosciences Corp. in Columbia, Maryland, chose a human gene called Glut1 that allows red blood cells to absorb glucose. When transplanted, the team reports in the 15 June issue of Science, it conferred that ability on microalgae.
To Apt's surprise, no more engineering was necessary, since the newly equiped microalgae could grow as fast in the dark as they did in sunlight. Apparently, the microalgae already contained the cellular machinery necessary to process the glucose efficiently. Apt hopes to apply his discovery to commercially useful microalgae species--but other species may not be as cooperative. "I don't expect it's going to be so simple in every case," he says.
"Biology is full of surprises," says chemical engineer Gregory Stephanopoulos of the Massachusetts Institute of Technology of the finding that a photosynthetic organism could thrive on sugar. Although he calls the work "encouraging," he echoes Apt in suspecting that a single gene won't have as dramatic an effect on other photosynthetic organisms.