Gram-Positive Bacteria: Possible Photosynthetic Ancestry

Abstract

A 16S rRNA gene was sequenced from Heliobacterium chlorum, the recently discovered photosynthetic bacterium that contains a novel form of chlorophyll. Comparisons with other 16S rRNA sequences show that the organism belongs to the gram-positive bacteria more precisely to the so-called low G + C (G, guanine; C, cytosine) subdivision thereof. This brings to 5 the number of such phyla that contain photosynthetic species, the other 4 being the purple bacteria and relatives, the green sulfur bacteria, the green nonsulfur bacteria and the cyanobacteria. The finding suggests that gram-positive bacteria may be of photosynthetic ancestry and it strengthens the case for a common photosynthetic ancestry for all eubacteria.