Heliobacterium
Heliobacillus
Heliophilum
Heliorestis The heliobacteria are a small family of bacteria that produce energy through photosynthesis. The primary pigment involved is bacteriochlorophyll g, which is unique to the group and absorbs at different frequencies than other photosynthetic pigments, giving the heliobacteria their own environmental niche. Photosynthesis takes place at the cell membrane, which does not form folds or compartments as it does in many other groups.

RNA trees place the heliobacteria among the Firmicutes. Unlike most other members they do not have gram-positive stains, since their cell walls are thin, but they share the characteristic absence of an outer membrane. They are also similar in other respects, including the ability to form endospores. They are the only group related to the gram-positive bacteria that conduct photosynthesis.

Heliobacteria are heterotrophic, using energy from light or chemicals but relying exclusively on organic sources for carbon, and are exclusively anaerobic. Whereas most other photosynthetic bacteria are predominantly aquatic, heliobacteria have been found mostly in soils, especially rice paddies.