The role of quorum sensing and specific quorum-sensing dependent properties in the colonization and spoilage of carrot slices by Serratia plymuthica RVH1 was investigated. Disinfected carrot slices were inoculated by immersion in a bacterial suspension and then placed in a Petri dish with a shallow layer of the same bacterial suspension. Subsequently, visible spoilage of the air-exposed upper side of the slices and the evolution of bacterial numbers and pH of the surrounding suspension were recorded during 19 days. A knockout mutant in the N-acyl-homoserine lactone (AHL) synthase splI was clearly compromised in its ability to colonize the surface of the carrot and cause browning. Mutants deficient in the production of extracellular proteases and in butanediol fermentation were isolated, both regulated by quorum sensing. The protease-deficient mutant (lipB) was not affected in the carrot slice spoilage assay. Since RVH1 does not produce pectinolytic enzymes, this suggests that hydrolytic enzymes do not play a major role in produce spoilage by this organism. On the other hand, a budB mutant with inactive butanediol fermentation pathway showed strongly enhanced growth on the carrot slices, in spite of a reduced survival in the surrounding medium.
|Journal||International Journal of Food Microbiology|
|State||Published - Aug 2009|