The heliobacteria are phototrophic: they convert light energy into chemical energy by photosynthesis and they use a Type I reaction centerHeinickel and Golbeck 2007. The primary pigment involved is bacteriochlorophyll g, which is unique to the group and has a unique absorption spectrum; this gives the heliobacteria their own environmental niche.  Phototrophy takes place at the cell membrane, which does not form folds or compartments as it does in purple bacteria. Even though heliobacteria are phototrophic, they can grow without light by fermentation of pyruvate.