Methionine biosynthesis pathway genes affect curdlan biosynthesis of Agrobacterium sp. CGMCC 11546 via energy regeneration

Curdlan is a water-insoluble exopolysaccharide produced by Agrobacterium species under nitrogen starvation. The curdlan production in the AmdeA, AmetA, AmetH, and AmetZ mutants of methionine biosynthesis pathway of Agrobacterium sp. CGMCC 11546 were significantly impaired. Fermentation profiles of four mutants showed that the consumption of ammonia and sucrose was impaired. Transcriptome analysis of the AmetH and AmetZ mutants showed that numerous differentially expressed genes involved in the electron transfer chain (ETC) were significantly down-regulated, suggesting that methionine biosynthesis pathway affected the production of energy ATP during the curdlan biosynthesis. Furthermore, metabolomics analysis of the AmetH and AmetZ mutants showed that ADP and FAD were significantly accumulated, while acetyl-CoA was diminished, suggesting that the impaired curdlan production in the AmetH and AmetZ mutants might be caused by the insufficient supply of energy ATP. Finally, the addition of both dibasic sodium succinate as a substrate of FAD recycling and methionine significantly restored the curdlan production of four mutants. In conclusion, methionine biosynthesis pathway plays an important role in curdlan biosynthesis in Agrobacterium sp. CGMCC 11546, which affected the sufficient supply of energy ATP from the ETC during the curdlan biosynthesis.

Automated summary

Curdlan, a water-insoluble exopolysaccharide produced by Agrobacterium species under nitrogen starvation, was significantly impaired in AmdeA, AmetA, AmetH, and AmetZ mutants. The impaired curdlan production was associated with down-regulation of genes involved in the electron transfer chain (ETC) and accumulation of ADP and FAD in the AmetH and AmetZ mutants. Addition of dibasic sodium succinate and methionine restored curdlan production in the mutants, indicating the importance of the methionine biosynthesis pathway in energy ATP supply during curdlan biosynthesis.