[Construction and functional analysis of the crtl gene disruptant in Deinococcus radiodurans]

With the method of Polymerase Chain Reaction and homologous genetic recombination in vivo, the key gene encoding bacterial-type phytoene desaturase (Crtl) which controls the carotenoids biosynthesis pathway in the non-photosynthetic and extremely radioresistant bacterium Deinococcus radiodurans was deleted from the genome. The colorless mutant obtained was designated as M61. Survival rates of mutant strain and wild type strain were investigated under different doses of gamma-radiation and hydrogen peroxide. The results showed that the radioresistant activity of M61 reduced rapidly under ionization radiation, and it became more sensitive to the treatment of hydrogen peroxide especially to high concentration of hydrogen peroxide compared to that of wild type R1. Reverse Phase High Performance Liquid Chromatography (RP-HPLC) was used to investigate the carotenoid composition of wild type R1 and mutant M61. HPLC results exhibited that the deficient of crtl gene had important effect on pigment biosynthesis pathway, leading to inhibition of the biosynthesis of lycopene and other carotenoids in D. radiodurans. All the results indicated that crtl gene was a key gene controlling the biosynthesis of red carotenoid including lycopene in D. radiodurans. The roles of carotenoids in protecting the bacterial cell from damage by ionization radiation and hydrogen peroxide suggest that the carotenoids contribute to the defense system in D. radiodurans. This study is important for elucidating the radioresistant and antioxidant mechanism in which carotenoids are involved, and it will supply some ideas to the further investigation on the biosynthesis pathway and functions of carotenoids in D. radiodurans.