Trophic conversion
Certain microalgae have the natural ability to metabolize sugars, while others rely strictly on photosynthesis. As a result of genetic engineering, some obligate photoautotrophs, formerly unable to partake in a sweet diet, have been given a taste of heterotrophy through the introduction of hexose transporters. Volvox carteri was one of the first green algae to be transformed with the hexose/H+ symporter gene Hup1 from Chlorella and heterotrophic growth was verified by the assimilation of 14C-labeled glucose and glucosamine [ 52]. Similar trophic conversions have also been carried out in Chlamydomonas reinhardtii [ 53••] and the diatom Phaeodactylum tricornutum [ 54], each demonstrating a fundamental change in metabolism caused by a single gene.