Quorum sensing-dependent regulation and blockade of exoprotease production in Aeromonas hydrophila

• Published in: Infection and Immunity 1999-10, Vol.67 (10), p.5192-5199
• Main Authors: Swift, S, Lynch, M.J, Fish, L, Kirke, D.F, Tomas, J.M, Stewart, G.S.A.B, Williams, P
• Format: Article
• Language: English
• Subjects: 4-Butyrolactone - analogs & derivatives; 4-Butyrolactone - physiology; Aeromonas hydrophila; Aeromonas hydrophila - enzymology; Aeromonas hydrophila - pathogenicity; Bacteriology; Biological and medical sciences; Exopeptidases; Fundamental and applied biological sciences. Psychology; Growth, nutrition, cell differenciation; Metalloendopeptidases - metabolism; Microbiology; Molecular and Cellular Pathogenesis; Mutation; Peptide Hydrolases - biosynthesis; proteinases; Serine Endopeptidases - metabolism; Virulence
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.67.10.5192-5199.1999

In Aeromonas hydrophila, the ahyI gene encodes a protein responsible for the synthesis of the quorum sensing signal N-butanoyl-L-homoserine lactone (C4-HSL). Inactivation of the ahyI gene on the A. hydrophila chromosome abolishes C4-HSL production. The exoprotease activity of A. hydrophila consists of both serine protease and metalloprotease activities; in the ahyI-negative strain, both are substantially reduced but can be restored by the addition of exogenous C4-HSL. In contrast, mutation of the LuxR homolog AhyR results in the loss of both exoprotease activities, which cannot be restored by exogenous C4-HSL. Furthermore, a substantial reduction in the production of exoprotease by the ahyI+ parent strain is obtained by the addition of N-acylhomoserine lactone analogs that have acyl side chains of 10, 12, or 14 carbons. The inclusion of N-(3-oxododecanoyl)-L-homoserine lactone or N-(3-oxotetradecanoyl)-L-homoserine lactone at 10 micromolar in overnight cultures of A. hydrophila abolishes exoprotease production in azocasein assays and reduces the activity of all the exoprotease species seen in zymograms.