Find in Library

Biofilm formation is a survival strategy by which microorganisms adapt to environmental challenges. It is regulated by various signals, such as the second messenger <i>c</i>-di-GMP. We previously found that the Flm chemosensory pathway could respond to chemical signals and regulate biofilm formation. This regulation is independent of <i>c</i>-di-GMP. A previous study revealed that the response regulator FlmD is involved in biofilm formation; however, how chemical signals are transmitted downstream of FlmD remained unclear. In the present study, transcriptome analysis and gel shift assay reveal that SoxR, a transcriptional activator of the efflux transporter <i>acrAB-tolC</i> operon, mediates the downstream signaling of FlmD. Phosphorylated FlmD interacts with SoxR and disrupts the interaction between SoxR and the <i>acrAB-tolC</i> operon. It causes a decrease in the expression of <i>acrAB-tolC</i> operon. The downregulation of <i>acrA</i>, <i>acrB</i>, or <i>tolC</i> gene expression results in making less biofilm formation. In conclusion, we identified that the transcription regulator SoxR plays a role in the <i>c</i>-di-GMP independent regulation of biofilm formation in <i>Comamonas testosteroni</i>.