The Transcription Factor CsgD Contributes to Engineered Escherichia coli Resistance by Regulating Biofilm Formation and Stress Responses.

The high cell density, immobilization and stability of biofilms are ideal characteristics for bacteria in resisting antibiotic therapy. CsgD is a transcription activating factor that regulates the synthesis of curly fimbriae and cellulose in Escherichia coli , thereby enhancing bacterial adhesion and promoting biofilm formation. To investigate the role of CsgD in biofilm formation and stress resistance in bacteria, the csg D deletion mutant Δ csg D was successfully constructed from the engineered strain E. coli BL21(DE3) using the CRISPR/Cas9 gene-editing system. The results demonstrated that the biofilm of Δ csg D decreased by 70.07% ( p < 0.05). Additionally, the mobility and adhesion of Δ csg D were inhibited due to the decrease in curly fimbriae and extracellular polymeric substances. Furthermore, Δ csg D exhibited a significantly decreased resistance to acid, alkali and osmotic stress conditions ( p < 0.05). RNA-Seq results revealed 491 differentially expressed genes between the parent strain and Δ csg D, with enrichment primarily observed in metabolism-related processes as well as cell membrane structure and catalytic activity categories. Moreover, CsgD influenced the expression of biofilm and stress response genes pga A, mot B, fim A, fim C, ira P, omp A, osm C, suf E and ela B, indicating that the CsgD participated in the resistance of E. coli by regulating the expression of biofilm and stress response. In brief, the transcription factor CsgD plays a key role in the stress resistance of E. coli , and is a potential target for treating and controlling biofilm.