Abstract:[Objective] To realize in vitro biosynthesis and activity detection of quorum sensing signal molecule autoinducer 2 (AI-2) of Aeromonas hydrophila. [Methods] LuxS, MtnN-1, MtnN-2 proteins were analyzed for amino acid sequences, expressed and purified. AI-2 was synthesized from S-adenosylhomocysteine (SAH) with purified LuxS and MtnN-1, or purified LuxS and MtnN-2 separately. The activity of AI-2 was detected by the reporter strain Vibrio harveyi BB170. [Results] The activity of AI-2 in A. hydrophila culture supernatant was 16.96-fold of the control at 8 h. As analysis of amino acid sequence alignment indicated, the identity of LuxS of A. hydrophila with that of V. harveyi and Edwardsiella tarda is above 76%. The identity of MtnN-1 with MtnN-2 is 26.37%. MtnN-2 has relatively high homologies with representative Pfs amino acid sequences. The identity of MtnN-2 with that of V. harveyi and E. tarda is above 53%. LuxS, MtnN-1 and MtnN-2 proteins were successfully expressed and purified. The activity of AI-2 produced with purified LuxS and MtnN-1 in vitro was 45.04-fold of the control; the activity of AI-2 produced with purified LuxS and MtnN-2 in vitro was 63.62-fold of the control. [Conclusion] A. hydrophila could secrete AI-2. MtnN-1 and MtnN-2 could both cooperate with LuxS and realize in vitro biosynthesis of AI-2, though the amino acid sequences between the two showed relatively big differences.
