CLUSTERING OF GENES WITH FUNCTION IN THE BIOSYNTHESIS OF BACTERIOCHLOROPHYLL AND HEME IN THE GREEN SULFUR BACTERIUM CHLOROBIUM VIBRIOFORME

identical to the pathway of heme biosynthesis (Fig. 1). The formation of 5- aminolevulinate can be achieved either from glycine and succinyl-CoA, in a reaction catalyzed by the enzyme 5-aminolevulinic acid synthase, or by a three step pathway from glutamate catalyzed by three enzymes, of which the second is glutamyl- tRNA dehydrogenase ( BEALE 1995). The succinyl- CoA pathway is used by nonplant eukaryotes and a group of bacteria that includes the purple photo- synthetic bacteria