Photosynthesis is how plants and some other life forms use sunlight to grow.
Dr. Splicer is trying to learn what kinds of proteins are important in photosynthesis. It turns out that not only plants but a few bacteria are able to use sunlight as an energy source. The process is actually very similar in plants and bacteria, but it is much easier to make mutants in the bacteria, so Dr. Splicer uses bacteria for his research. He has found three mutants which all seem to change how well photosynthesis works. He thinks that in these mutants some of the proteins used during photosynthesis have been changed.