Screening Of A Strain Of Photosynthetic Bacteria With High 5-aminolevulinic Acid Production And Cloning Of 5-aminolevulinic Acid Synthase

5-Aminolevulinic (5-ALA) is a derivative of 5-carbon amino acid and is found in most living organisms,more and more sciencists pay attention to its applications in agriculture and medical . Photosynthetic bacteria are the earliest protist that have original photosynthetic system . They are easy to be cultured and no toxin and have the high extra-cellular production of 5-ALA.Biological ALA synthesis proceeds by two distinct pathways: C-4 pathway and C-5 pathway, the former is existed in purple non-sulfur photosynthetic bacteria. 5-Aminolevulinic acid synthase (ALAS), the first enzyme of the heme biosynthesis pathway, is encoded from hemA in the genus Rhodopseudomonas.In this study, the productions of 5-ALA by 20 photosynthetic bacteria strains from different habitats were determined. Strain R5 was screened out.Its morphology and ability to utilize different carbon sources were studied.A phylogenetic tree was constructed by the neighbour joining method based on the sequence of 16S rRNA fragment. Moreover, the hemA gene fragment was amplified and cloned from Strain R5 and sequenced.Strain R5 isolated from the bottom mud of a pond in Yunxi park, GuangZhou, had the highest production of 5-ALA (4.92mg/L). Its morphology and physiologyical- biochemical characteristic are consistented with the species of the genus Rhodopseudomonas. The phylogenetic tree showed that strain R5 was clustered with Rhodopseudomonas palustrisKUGB306, with homology being 99%. Strain R5 with the highest production of 5-ALA should therefore be classified in the genus Rhodopseudomonas. The deduced amino acid sequence of hemA showed 100% sequence identity from Rhodopseudomonas palustrisKUGB306, the work lays the foundation for obtaining genetically engineered photosynthetic bacteria for the overproduction of 5-aminolevulinic acid.