Many Proteobacteria synthesize acyl-homoserine lactone (AHL) molecules for use 
as signals in cell density-dependent gene regulation known as quorum sensing 
(QS) and response. AHL detection protocols are essential to QS researchers and 
several techniques are available, including a 14C-AHL radiolabel assay. This 
assay is based on the uptake of radiolabeled methionine by living cells and 
conversion of the radiolabel into S-adenosylmethionine (SAM). The radiolabeled 
SAM is then incorporated into AHL signal by an AHL synthase enzyme. Here we 
describe a methodology to perform the AHL radiolabel assay, which is unbiased, 
relatively fast, and very sensitive compared to other AHL detection protocols.