micromolar concentrations. The third section describes theC.
violaceumAHL bioassay for detecting C4- and C6-HSLs on the
basis of pigment induction in the reporter strain, CVO26. The
fourth section describes a pigmentation inhibition assay, using the
type strain 12472, which can be used as an indirect detection
approach for other AHLs (other than C4- or C6-HSLs). Alterna-
tively this fourth approach can be used as an initial screen for QS-
inhibiting compounds or AHL-degrading (quorum-quenching)
enzymes [33]. The fifth section describes a thin-layer chromatog-
raphy (TLC) protocol that can be used to detect AHLs [38]. Here,
A. tumefaciensA136 (pCF218)(pCF372) is typically used as a
biosensor (Fig.5).Fig. 2Inoculation strategies for bioassays on Petri plates. (a) shows inoculation
of a test organism prior to an overlay assay (Subheading3.2.2). (b) and (c) show
the inoculation pattern of a test organism or extract (patterned small circle) and
varied location of AHL-producing (dashed line) and AHL-detecting (solid line)
strains to differentiate interference with AHL production or AHL response (details
in Subheading3.2.3). (d) shows an inoculation strategy for high-throughput
screens of test organisms (indicated bynumbers) near a bioassay organism
(solid line)8 Starla G. Thornhill and Robert J.C. McLean