Improving the chitinolytic activity of streptomyces griseorubens E44G by mutagenesis

Abstract

Genetic improvement trials of the chitinolytic activity of Streptomyces griseorubens E44G were made by using physical, chemical and site-directed mutagenesis. Although the UV radiation, as a physical mutagen, was shed on the tested bacteria for different durations (5, 10, and 15 min), no change in the chitinolytic activity was observed when compared with the wild type. To induce the chemical mutagenesis, S. griseorubens E44G was treated with ethylmethane sulfonate for varied durations (20, 40, and 60 min). The chitinolytic activity decreased with the increment in the exposure period. Four different sets of primers were designed based on the DNA sequence of the wild type of S. griseorubens E44G.Overexpressionof chitinase-encoding genes was observed as three of the amplified mutated genes comparing with the wild-type gene. The chitinolytic activity of the recombinant gene P2 increased by 1.39-fold comparing with the wild-type gene. The molecular weight of the chitinase protein produced by the mutated gene was determined by SDS-PAGE. In conclusion, these results demonstrated that the recombinant gene of S. griseorubens E44G possess a higher level of chitinolytic activity than that of the wild-type. Genetic improvement of the chitinolytic activity of S. griseorubens E44G may enhance their biocontrol potential against phytopathogenic fungi.