violaceum CV026 and incubated. A purple halo indicates the presence of 3-oxo-C6-HSL. Characterization of QQ Activities of Acinetobacter GG2, Burkholderia GG4 and Klebsiella Se14 To determine the range of AHLs inactivated by each of the three ginger rhizosphere isolates, whole cells resuspended in PBS buffer were incubated for up to 96 h with a range of AHLs differing in acyl chain length (C4-C14), the presence or absence of a C3 substituent (oxo or hydroxy)

or with a series of 3-hydroxy-C14-HSLs with a double bond at either C9, C10, C11 or C13 (Table 1). After incubation, AZD3965 any remaining AHLs were detected using the appropriate AHL biosensor as described in the Methods section and compared with Escherichia coli DH5α and PBS as negative controls. The data obtained are summarized in Table 1. Using biosensor assays Klebsiella Se14 inactivated all of the AHLs tested while Acinetobacter GG2 showed broad activity but was most effective against the long chain unsubstituted or 3-hydroxy substituted saturated or unsaturated acyl chain-AHLs (Table 1). Burkholderia GG4 exhibited no apparent activity against the AHLs using these biosensor

assays (data not shown). Table 1 AHLs degraded by GG2 and Se14 Types of AHL tested AHL-degradation pattern   GG2 Se14 C4-HSL + + + + C5-HSL + + + + + C6-HSL + + + + + C7-HSL + + + + + C8-HSL + + + + + C9-HSL + + + + + + C10-HSL + + + + + + C11-HSL + + + + + + C12-HSL + + + + + + C14-HSL + + + + + + 3-hydroxy-C4-HSL + + + SC75741 mw + + 3-hydroxy-C6-HSL + + + + + 3-hydroxy-C8-HSL + + + + + 3-hydroxy-C10-HSL + + + + + + 3-hydroxy-C12-HSL + + + + + + 3-hydroxy-C14-HSL + + + + + + 3-oxo-C8-HSL + + + + + 3-oxo-C10-HSL + + + + + 3-oxo-C12-HSL + + + + + 3-oxo-C14-HSL + + + + + Δ9-3-hydroxy-C14-HSL + + + + + + Δ10-3-hydroxy-C14-HSL + + + + + + Δ11-3-hydroxy-C14-HSL + + + + + + Δ13-3-hydroxy-C14-HSL + + + + + + Degradation of AHLs by GG2 and Se14. Degradation of AHL: + : weak; ++ : moderate; + + + : significant. Insets denote the digital image of AHLs detected

using the biosensors E. coli [pSB401] and/or E. coli [pSB1075]; evaluated according to the reduction in bioluminescence. All experiments took into account the detection for limit of the biosensors used for each AHL-degradation assay. Since natural AHLs are in the L-configuration, we sought to determine whether the AHL inactivating activities observed were stereospecific. After incubation of GG2 and Se14 whole cells with the D-isomer of XAV-939 order 3-oxo-C6-HSL (3-oxo-C6-D-HSL), the reaction mixture was extracted and analysed by HPLC rather than using the AHL biosensors which do not respond to D-isomers. For GG2 and Se14 the peak corresponding to 3-oxo-C6-D-HSL was reduced after 3 h incubation and effectively absent after 24 h. The data for Acinetobacter strain GG2 are shown in Figure 2A. Similar results were obtained for Se14 (data not shown) indicating that AHL inactivation by these two ginger rhizosphere bacteria is not stereospecific.