biostudies-literatureGao MNIGMS NIH HHS7931-44https://www.ebi.ac.uk/biostudies/studies/S-EPMC1291280biostudies-literatureUnknown187(23)Quorum sensing (QS) in Sinorhizobium meliloti, the N-fixing bacterial symbiont of Medicago host plants, involves at least half a dozen different N-acyl homoserine lactone (AHL) signals and perhaps an equal number of AHL receptors. The accumulation of 55 proteins was found to be dependent on SinI, the AHL synthase, and/or on ExpR, one of the AHL receptors. Gas chromatography-mass spectrometry and electrospray ionization tandem mass spectrometry identified 3-oxo-C(14)-homoserine lactone (3-oxo-C(14)-HSL), C(16)-HSL, 3-oxo-C(16)-HSL, C(16:1)-HSL, and 3-oxo-C(16:1)-HSL as the sinI-dependent AHL QS signals accumulated by the 8530 expR(+) strain under the conditions used for proteome analysis. The 8530 expR(+) strain secretes additional, unidentified QS-active compounds. Addition of 200 nM C(14)Journal of bacteriologysinI- and expR-dependent quorum sensing in Sinorhizobium meliloti.PMC1291280R01 GM042893Robinson JBGao MEberhard AGronquist MRChen HRolfe BGBauer WDfalsesinI- and expR-dependent quorum sensing in Sinorhizobium meliloti.Quorum sensing (QS) in Sinorhizobium meliloti, the N-fixing bacterial symbiont of Medicago host plants, involves at least half a dozen different N-acyl homoserine lactone (AHL) signals and perhaps an equal number of AHL receptors. The accumulation of 55 proteins was found to be dependent on SinI, the AHL synthase, and/or on ExpR, one of the AHL receptors. Gas chromatography-mass spectrometry and electrospray ionization tandem mass spectrometry identified 3-oxo-C(14)-homoserine lactone (3-oxo-C(14)-HSL), C(16)-HSL, 3-oxo-C(16)-HSL, C(16:1)-HSL, and 3-oxo-C(16:1)-HSL as the sinI-dependent AHL QS signals accumulated by the 8530 expR(+) strain under the conditions used for proteome analysis. The 8530 expR(+) strain secretes additional, unidentified QS-active compounds. Addition of 200 nM C(14)2005-01-01T00:00:00Z2005 Dec2025-04-04T09:51:38.596Z2025-02-19T04:02:07.515ZS-EPMC12912801629166610.1128/jb.187.23.7931-7944.200510.1128/JB.187.23.7931-7944.2005