Identification of immune inhibitor from Pseudomonas aeruginosa of inducible cell-free antibacterial activity in insects.

Insect-pathogenic strains of Pseudomonas aeruginosa produce specific proteinase which selectively degrades the cecropin-based defence system of insects. This was demonstrated by the disappearance of the Galleria cecropin and purified Hyalophora cecropin B peptide PAGE bands, but not the lysozyme band, upon exposure to infected extracts and a similar abrogation of antibacterial activity using an agar diffusion assay. In addition, the proteolytic activity of infected extracts produced by high and low virulence Pseudomonas strains was shown to be correlated with cecropin-inhibitory activity. This indicated that the bacterial proteinase was responsible for the ability of bacteria to establish infections and strain virulence.