QUORUM SENSING IN VIBRIO-FISCHERI - PROBING AUTOINDUCER-LUXR INTERACTIONS WITH AUTOINDUCER ANALOGS

The Vibrio fischeri luminescence genes are activated by the transcript ion factor LuxR in combination with a diffusible signal compound, N-(3 -oxohexanoyl) homoserine lactone, termed the autoinducer, We have synt hesized a set of autoinducer analogs, Many analogs with alterations in the acyl side chain showed evidence of binding to LuxR. Some appeared to bind with an affinity similar to that of the autoinducer, but none showed a higher affinity, and many did not bind as tightly as the aut oinducer. For the most part, compounds with substitutions in the homos erine lactone ring did not show evidence of binding to LuxR, The excep tions were compounds with a homocysteine thiolactone ring in place of the homoserine lactone ring, Many but not all of the analogs showing e vidence of LuxR binding had some ability to activate the luminescence genes, None were as active as the autoinducer, While most showed littl e ability to induce luminescence, a few analogs with rather conservati ve substitutions had appreciable activity. Under the conditions we emp loyed, some of the analogs showing little or no ability to induce lumi nescence were inhibitors of the autoinducer.