Overexpression And Function Exploration Of Quorum Sensing Gene LuxR In Gluconacetobacter Xylinus CGMCC 2955

In recent years, bacterial cellulose due to its high purity, as well as excellent properties such as high hydrophilicity, high biocompatibility and well mechanical properties is widely used in various industries, such as biological medicine industry,papermaking industry, as well as the food industry. Gluconacetobacter xylinus as the pattern strain of bacterial cellulose production, the mechanism of bacterial cellulose production is still unclear. Our lab confirmed that G.xylinus CGMCC 2955 has a LuxI/LuxR like quorum sensing system as Vibrio fischer.A large number of literatures indicate that quorum sensing is related to the synthesis of biofilm, in this paper, we studied the relationship between the quorum sensing system and bacterial cellulose synthesis.This study through molecular biology means to construct the quorum-sensing key genes luxR overexpress vector,then introduced intoG.xylinus by eletroporation,through static culture and agitated culture to compare the fermentation properties between original strain and overexpress strains, as well the differences of structure of different bacterial cellulose produced by different strains.The results showed that under agitated culture, compared with the original strain, G.x-pMV24-luxR grewslower significantly, at the end of fermentation, the biomass was 15.51% lower than original strain, the gluconic acid yield increased by 12.11%, utilization of glucose acid increased by 20.18%, but no obvious difference was found between the total acid production. In static condition,compare to original strains,production of bacterial cellulose produced by G.x-pMV24-luxR increased by 36.45%, gluconic acid content of G.x-pMV24-luR in 16d was 23.68% lower than the original strains. Comparing the characteristics of various bacterial cellulose produced by different strains,For FT-IR analysis,as differences exist in the non-crystalline region,shows that structure has no significant difference; XRD analysis indicates that cellulose of G.x-pMV24-luxR has significantly lower crystallinity than another; TG/DTG shows cellulose of G.x-pMV24-luxR has a lower thermal stability.Based on gas chromatography - mass spectrometry (GC-MS) of metabonomics,analysis intracellular small molecule metabolites between original strain and G.x-pMV24-luxR, explore how the quorum sensing effects on intracellular metabolism.Results showed that the overexpression of luxR have an effect on carbon metabolism,amino acid metabolism, lipid metabolism. as well repressed aerobic fermentation,results in a large number of glucose acid synthesis,as well improve the purine pyrimidine denovo synthesis, but inhibit the amino acids metabolism, For protecting the cells, trehalose as a kind of cell protective material, has a notable increase with a vast amount of synthetic glucose acid at the same time.