Boron Derivatives Accelerate Biofilm Formation of Recombinant Escherichia coli via Increasing Quorum Sensing System Autoinducer-2 Activity.

Boron is an essential element for autoinducer-2 (AI-2) synthesis of quorum sensing (QS) system, which affects bacterial collective behavior. As a living biocatalyst, biofilms can stably catalyze the activity of intracellular enzymes. However, it is unclear how boron affects biofilm formation in E. coli , particularly recombinant E. coli with intracellular enzymes. This study screened different boron derivatives to explore their effect on biofilm formation. The stress response of biofilm formation to boron was illuminated by analyzing AI-2 activity, extracellular polymeric substances (EPS) composition, gene expression levels, etc. Results showed that boron derivatives promote AI-2 activity in QS system. After treatment with H 3 BO 3 (0.6 mM), the AI-2 activity increased by 65.99%, while boron derivatives increased the biomass biofilms in the order H 3 BO 3 > NaBO 2 > Na 2 B 4 O 7 > NaBO 3 . Moreover, treatment with H 3 BO 3 (0.6 mM) increased biomass by 88.54%. Meanwhile, AI-2 activity had a linear correlation with polysaccharides and protein of EPS at 0-0.6 mM H 3 BO 3 and NaBO 2 (R 2 > 0.8). Furthermore, H 3 BO 3 upregulated the expression levels of biofilm formation genes, quorum sensing genes, and flagellar movement genes. These findings demonstrated that boron promoted biofilm formation by upregulating the expression levels of biofilm-related genes, improving the QS system AI-2 activity, and increasing EPS secretion in E. coli .