Studies Of Breeding High-yield 5-aminolevulinic Acid Mutant Strain Of Rhodobacter Sphaeroides By Low Energy Ion Implantation

5-aminolevulinic acid(ALA) can be used as a non-pollution herbicide,insecticide, photodynamic agent,antimicrobial drug,and accelerant of plant growth.Microbial producyion of ALA may be expected to become commercially viable because of simple process and high production,so it is attended by researchers and enterprises.In this paper,through 20keV Ar⁺ implanting into Rhodobacter sphaeroides to obtain high-yield mutant.Simultaneously,the cultivating condition of the mutain strain was optimized.In order to compare differences between the original strain and the mutain strain in the molecular level,PCR technology and methods of bioinformatics were adopted to analysis the molecular transformation of the mutain strain.The results were as follows:1 Use 20keV,0.26×10¹⁵ ions/cm²ï½ž2.47×10¹⁵ ions/cm² doses Ar⁺ dealing with the the original strain Rhodobacter sphaeroides.After the analysis of survival and mutant rates and through three screens,a high-yield mutant strain R_B was obtained. The best ion implatation dose is 1.30×10¹⁵ ions/cm².2 After several multiplying,the results are as follows:the genetic of high-yield mutant strain is stable.The ALA production of the mutant strain Rhodobacter sphaeroides(R_B) is 9.23 g/L,which was 2.44 times than that of the original.3 The optimal ALA production condition of the mutant strain Rhodobacter sphaeroides(R_B) is pH7.0,10%volume of seeds,30001ux of illumination inten -sity,ALA production of R_B was the highest.4 The gene hemA were amplified from RB using primers designed according to the original sequence and sequences analysis were investigated.It was found that there were 36 base sites and 7 aminoacids in the aminoacid sequences of hemA changed. Transition was more than transversion in the base mutation.The frequence of transition was 69.4%,but that of transversion was 30.6%.Base and aminoacid mutations of hemA may be the reasons for the increasing of activity.This laid the foundation for the further analysis of which the high-yield molecular mechanism of ALA.