Uses a Nonpathogenic Streptomyces Species to Produce Industrial-Scale Thaxtomin for Herbicidal Applications
Thaxtomin is a toxin produced by Streptomyces species of bacteria that causes plant cell death by inhibiting the synthesis of cellulose, the major component of a plant’s cell wall. This naturally occurring toxin is a desirable candidate to develop into an organic herbicide for weed control. However, a major impediment to commercializing thaxtomin is that the species of Streptomyces that produces this toxin is pathogenic and the levels of thaxtomin produced fall well below what is needed for cost-effective manufacture.
Researchers at the University of Florida have succeeded in transferring the cluster of genes responsible for biosynthesis of thaxtomin into a nonpathogenic Streptomyces strain. Additionally, they have engineered the gene cluster to eliminate the need to use an expensive component of culture media previously required to promote thaxtomin biosynthesis. The end result is nonpathogenic Streptomyces strains capable of producing thaxtomin at levels that make commercial production far more cost-effective.
Engineered nonpathogenic Streptomyces species that produces thaxtomin in higher yields, making commercial production more cost-effective
- Utilizes a nonpathogenic strain of Streptomyces species to produce thaxtomin, avoiding safety concerns associated with pathogenic Streptomyces species
- Produces much higher levels of thaxtomin, leading to lower, more cost-effective production
Streptomyces scabiei is a plant pathogen that kills host cells with thaxtomin, a secreted toxin. A biosynthetic gene cluster located on a mobile genomic island enables and regulates the production of thaxtomin. UF scientists mated S. scabiei with nonpathogenic Streptomyces species, which resulted in the acquisition of the thaxtomin biosynthetic cluster by nonpathogenic Streptomyces species. Most of the recipient Streptomyces species either did not produce thaxtomins or produced lower amounts than S. scabiei upon the acquisition of the thaxtomin cluster, indicating that the genetic backgrounds of recipients affect thaxtomin production considerably. However, S. albus J1074 produced a significantly higher concentration of thaxtomins in comparison to S. scabiei, and the engineered strain is suitable for the heterologous production of thaxtomin for commercial applications. Additionally, researchers refactored the biosynthetic gene cluster and controlled the expression of the cluster to exclude cellobiose in thaxtomin production, greatly reducing production costs.