Fig. 4.

C78 is the key residue for LqqP in inhibiting the production of AHL in P. fluorescens 2P24. (A) The distribution of LqqP homologs in selected bacterial species with or without AHL-producing ability. Nine LqqP homologous genes highlighted in red were selected for heterogeneous expression in 2P24 and the red underline represents their ability to block AHL production; (B) The expression of nine LqqP homologous genes in 2P24 in blocking AHL production. lqqP and gfp were used as positive and negative controls, respectively. (C) AHL quantification corresponding to panel B. (D) The sequence alignment of LqqP from L. enzymogenes OH11 and its homologue, GLE4458 from L. enzymogenes C3. The arrows indicate the nine different amino residues between LqqP and GLE4458. (E-F) The effect of heterogeneous expression of LqqP variants genes with site mutations on the production of AHL in 2P24. Single site mutations or combinations are shown in in red. The AHL production in plates and its quantification are displayed in the upper and lower panels, respectively. lqqP and gfp were used positive and negative controls, respectively. The average data from three experiments is displayed, ± SD. ***P < 0.0001 relative to 2P24 expressing gfp. “ns” stands for not statistically significant. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)