"Photolithotrophic growth requires light and an inorganic electron donor and is usually associated with the ability to use carbon dioxide as the sole source of carbon, i.e., photoautotrophy. Many of these organisms require specific growth factors, usually the vitamins B12, biotin, or thiamine, which may be supplied in the very small amounts required, approximately 10^-6 mg/L, by other organisms capable of synthesizing them."
Now you see why I need the Celtics this year. 1st semester grad school is kicking my butt.