Abstract
Heliobacteria are strictly anaerobic, nitrogen fixing photosynthetic bacteria. On the basis of 16S rRNA sequence analysis, heliobacteria appear to be most closely related to Gram-positive bacteria, but also an evolutionary link to cyanobacteria is evident. Heliobacteria synthesize a unique photopigment, bacteriochlorophyll (BChl) g, which has an interesting structural similarity to chlorophyll (Chl) a from oxygenic phototrophs. BChl g contains an ethylidene side group at C8 of ring II that, in the presence of oxygen and light, isomerizes to produce an ethyl group, giving rise to a ring structure that is the same as in Chl a. A heliobacterium Heliobacillus mobilis contains a major cluster of photosynthesis genes which include genes involved in BChl and carotenoid biosynthesis and structural gene of reaction center apoprotein. We are investigating photosynthesis gene cluster from another species of heliobacteria, Heliophium fasciatum, and will discuss the comparison study of the photosynthesis gene cluster between heliobacteria.
