The

mass spectra of the extracted AHLs were similar to the corresponding synthetic compounds. Quantitative analysis by LC-MS/MS of the AHLs produced by GG2 over a 24 h period revealed that 3-hydroxy-C12-HSL was the most abundant AHL produced by GG2 which attains a maximum level after 12 h growth, but is almost undetectable GS1101 after 24 h (data not shown). Figure 3 Mass spectra of the AHLs produced by GG2. Extracts from spent culture supernatants of GG2 were analysed by LC-MS/MS. The fragment ion at m/z 102 is characteristic of the homoserine lactone ring (A and B). By comparison with the corresponding synthetic AHL standards (C and D) the precursor ion of m/z 298.2 and fragment ion of m/z 197.2 demonstrate the presence NSC 683864 research buy of 3-oxo-C12-HSL (A) whereas the precursor ion of m/z 282.2 (which corresponds to [M-H2O]) and fragment ion of m/z 181.2 are characteristic for 3-hydroxy-C12-HSL (B). AU: Absorbance unit. LC-MS/MS analysis of GG4 supernatants confirmed the presence of 3-oxo-C6-HSL (precursor ion m/z 214.2 [M+H]; fragment ions m/z 113.0, 102.0); C8-HSL (precursor ion m/z 228.2 [M+H]; fragment ions m/z 109.1, 102.0), 3-hydroxy-C8-HSL (precursor ion m/z 226.2 [M-H2O]; fragment ions m/z 125.1, 102.0) and C9-HSL (precursor ion m/z 242.2 [M-H2O]; fragment ions m/z 142.2, 102.1) (Additional File 1). The mass

spectra of the extracted AHLs were indistinguishable from the corresponding synthetic compounds (Additional File 1). QQ biocontrol activity of the ginger rhizosphere isolates To determine whether any of the three ginger rhizosphere bacterial isolates were capable of quenching virulence factor production in human (P. aeruginosa) and plant (Er. carotovora) Levetiracetam pathogens which utilize different AHLs, we undertook GS-9973 co-culture experiments. Figure 4A shows that Acinetobacter GG2 and Burkholderia GG4 both reduced elastase production approximately two-fold when compared to the P. aeruginosa PAO1 control whereas

the Klebsiella strain Se14 was the most effective, reducing elastase levels about 16-fold. None of the QQ bacteria inhibited the growth of P. aeruginosa which reached a similar viable count in co-culture as was attained in monoculture (data not shown). GG2 and Se14 both effectively reduced the expression of lecA in P. aeruginosa although GG4 had comparatively little effect (Figure 4B). Figure 4 Quenching of elastase production and lecA expression in P. aeruginosa by ginger rhizosphere strains. (A) Elastase production by P. aeruginosa following monoculture (PAO1) or in co-culture with GG2 (PAO1+GG2), GG4 (PAO1+GG4) or Se14 (PAO1+Se14) at a starting inoculum ratio of 1:1 for 24 h. (B) Expression of a lecA::lux fusion following monoculture or co-culture of P. aeruginosa PAO1 with GG2, GG4 or Se14 at a starting inoculum ratio of 1:1 for 24 h. The data are presented as RLU/OD to account for any differences in growth. The QQ potential of GG2, GG4 and Se14 for attenuating the 3-oxo-C6-HSL-dependent pectinolytic activity of Er.