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pubmed:abstractText |
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.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, Non-P.H.S.,
Research Support, Non-U.S. Gov't,
Evaluation Studies
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