title: Use of Sinorhizobium meliloti as an indicator for specific detection of long-chain N-acyl homoserine lactones.
abstract: Population-density-dependent gene expression in gram-negative bacteria involves the production of signal molecules characterized as N-acyl homoserine lactones (AHLs). The synthesis of AHLs by numerous microorganisms has been identified by using biosensor strains based on the Agrobacterium tumefaciens and Chromobacterium violaceum quorum-sensing systems. The symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti is rapidly becoming a model organism for the study of quorum sensing. This organism harbors at least three different quorum-sensing systems (Sin, Mel, and Tra), which play a role in its symbiotic relationship with its host plant, alfalfa. The Sin system is distinguished among them for the production of long-chain AHLs, including C(18)-HL, the longest AHL reported so far. In this work, we show that construction of a sinI::lacZ transcriptional fusion results in a strain that detects long-chain AHLs with exquisite sensitivity. Overexpression of the SinR regulator protein from a vector promoter increases its sensitivity without loss of specificity. We also show that the resulting indicator strain can recognize long-chain AHLs produced by unrelated bacteria such as Paracoccus denitrificans and Rhodobacter capsulatus. This S. meliloti indicator strain should serve as a tool for the specific detection of long-chain AHLs in new systems.
authors.affiliation: Department of Molecular and Cell Biology, University of Texas at Dallas, Richardson, TX 75083-0688, USA.
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Llamas
authors.forename: Neela
authors.initials: N
authors.lastname: Keshavan
authors.forename: Juan E
authors.initials: JE
authors.lastname: González
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001431:Bacteriological Techniques; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D005822:Genetic Vectors; D010231:Paracoccus denitrificans / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015398:Signal Transduction; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D011993:Recombinant Fusion Proteins; C097712:SinI protein, Bacillus subtilis; C088386:homoserine lactone; D015107:4-Butyrolactone