An order of photosynthetic, mainly aquatic, Gram-negative bacteria which contain special chlorophylls called bacteriochlorophylls. Photosynthesis occurs only in the absence of air, and oxygen is not released. Some species can also grow chemo-organotrophically in the presence of air. Families are Chlorobiaceae, Chloroflexaceae, Chromatiaceae, and Rhodospirillaceae.
Subjects: Plant Sciences and Forestry.