Autoinducer-2 regulates the chemotaxis and biofilm formation of Pseudomonas putida KT2440 by the methyl-accepting chemotaxis protein McpU

Abstract:

[Background] Autoinducer-2 (AI-2), ubiquitous in Gram-negative bacteria and Gram-positive bacteria, can mediate intraspecific and interspecific communication and regulate a variety of physiological processes. However, whether Pseudomonas putida KT2440 can sense AI-2 signal has not been reported yet. [Objective] To explore the chemotactic receptor mediating the chemotaxis of KT2440 to AI-2, and to detect the regulatory role of AI-2 in the biofilm formation of KT2440. [Methods] Firstly, soft agar plate assay and quantitative capillary assay were employed to detect the chemotactic response of KT2440 to AI-2. Then, the ligand binding domain (LBD) of the methyl-accepting chemotaxis protein McpU which had a high homology with that of the known AI-2 receptor TlpQ in Pseudomonas aeruginosa was expressed and purified. Vibrio harveyi MM32 bioluminescence and isothermal titration calorimetry (ITC) were adopted to detect the interaction between McpU-LBD and AI-2. Soft agar assay and quantitative capillary assay were carried out to evaluate the chemotaxis of the mcpU knockout strain (ΔmcpU) to AI-2. The effect of AI-2 on the biofilm formation of KT2440 and ΔmcpU was detected by crystal violet staining. [Results] KT2440 exhibited chemotaxis to AI-2. The bioluminescence and ITC assays showed that AI-2 bound to McpU-LBD with high affinity. The chemotaxis of KT2440 to AI-2 was mediated by McpU, and AI-2 significantly enhanced the biofilm formation in KT2440 via its receptor McpU (P<0.05). [Conclusion] McpU mediates the chemotaxis of P. putida KT2440 to AI-2, and AI-2 significantly enhances the biofilm formation of P. putida KT2440 by engaging McpU.