E homologs to all known chlorophyll a biosynthesis genes. The two proteins responsible for the biosynthesis of Chl a from protoporphyrin IX, magnesium-protoporphyrin IX monomethyl ester oxidative cyclase (AcsF) and chlorophyll synthase (ChlG) (30), are highly homologous to those in other cyanobacteria, including a common conserved duplication of acsF. This indicates that Chl d is likely synthesize