Photosynthetic humans–endowed with the power to derive energy from the sun–are a popular construct of science fiction. But Pamela Silver, a biologist at Harvard Medical School, aims to push that concept into reality.

Silver’s research focuses on cyanobacteria, a microbe responsible for almost 50 percent of the earth’s photosynthetic ability. Her team aims to harness the organisms’ photosynthetic powers by engineering them to generate fuel and other valuable chemicals.

But Silver is also experimenting with a more fantastical use for the microbes. In a recent experiment, researchers injected fluorescently labeled cyanobacteria into zebrafish embryos, a species commonly used in research. The fish are transparent, making them easy to observe during development. Much to Silver’s surprise, the fish survived and grew, as did the fluorescent microbes living inside their cells. “When we put E. coli into fish, they blew up, but they are extremely tolerant of cynabacteria,” Silver said at a synthetic biology conference in Boston last week, where she presented the research. Right now, the system doesn’t make enough energy to maintain the fish, but the researchers are experimenting with different engineering approaches to enhance production.

The video below shows Zebrafish embryos (green) that have been injected with photosynthetic cyanobacteria (red).

The ability to run on sunlight would certainly be a handy superpower. But what if you still like to eat? James Liao, a biologist at UCLA, has developed a new strategy to enhance cells’ ability to burn fat by adding a metabolic pathway from bacteria and plants. (For more details, see Making Fat Disappear.) “Female mice show a huge decrease in diet-induced obesity, and they accumulate much less fat,” said Liao at the conference. Results for male mice are less dramatic, though it’s not clear why.