Abstract
The luxS gene is required for autoinducer-2 (AI-2) synthesis in many bacterial species. AI-2 is taken up by a specific receptor to regulate multiple bacterial activities. However, the lack of methods to identify AI-2 receptors has impeded investigations into the roles of AI-2. Here, a luxS mutant of Escherichia coli strain BL21 (DE3) was constructed (named BL21∆luxS), and the recombinant LsrB protein of Salmonella enterica was expressed in BL21∆luxS and BL21 cells, which were named LsrB (BL21∆luxS) and LsrB (BL21), respectively. The results of the activity of recombinant LsrB binding showed that LsrB (BL21) bound to endogenous AI-2 (produced from BL21 strain), while LsrB (BL21∆luxS) did not (as BL21∆luxS cannot produce AI-2). However, the results of recombinant LsrB binding showed that LsrB (BL21∆luxS) can bind exogenous AI-2, which was released from LsrB (BL21∆luxS) at 55 °C for 10 min, while LsrB (BL21) could not bind exogenous AI-2 (due to binding of endogenous AI-2 before). Furthermore, analysis of the thermal stability of AI-2 showed that that AI-2 activity was relatively high at incubation temperatures below 65 °C. These findings will be beneficial for screening of new AI-2 receptors in different bacterial species.
Highlights
Cell–cell communication in bacteria is accomplished through the exchange of extracellular signalling molecules, called autoinducers, in a process termed quorum sensing (QS) (Pereira et al 2013)
The results of recombinant LsrB binding showed that LsrB (BL21∆luxS) can bind exogenous AI-2, which was released from LsrB (BL21∆luxS) at 55 °C for 10 min, while LsrB (BL21) could not bind exogenous AI-2
The BL21ΔluxS mutant strain lacked AI‐2 activity No AI-2 activity was detected from bacterial culture fluid (CF) prepared from mutant strain BL21ΔluxS, in which the luxS gene was deleted (Fig. 2)
Summary
Cell–cell communication in bacteria is accomplished through the exchange of extracellular signalling molecules, called autoinducers, in a process termed quorum sensing (QS) (Pereira et al 2013). Some bacterial species lack the AI-2 synthase gene luxS and are, not capable of producing AI-2 (De Keersmaecker et al 2006; Rezzonico and Duffy 2008) Such bacteria, including Sinorhizobium meliloti (Pereira et al 2013) and Riemerella anatipestifer (Han et al 2015a, b), might use endogenous AI-2 to regulate physiological functions. A set of criteria was established to identify functional AI-2 receptors using LsrB in S. typhimurium. These findings will be beneficial for future screening of AI-2 receptors in different bacterial species
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