Well-known quorum sensing inhibitors do not affect bacterial quorum sensing-regulated bean sprout spoilage

To investigate the potential of quorum sensing inhibitors (QSI) as food preservative agents in a food product, where bacterial spoilage is controlled by quorum sensing (QS). The effects of well-known QSI were tested on spoilage phenotypes and on QS-regulated genes of a bean sprout spoiling bacterial isolate (Pectobacterium A2JM) in laboratory substrates and in a bean sprout model system.

The acylated homoserine lactones (AHL) analogues PenS-AHL and HepS-AHL decreased the specific protease activity of Pectobacterium A2JM in broth but did not reduce the expression of a QS-regulated secretion protein, and were without effect on soft rot of bean sprouts. The QSI ProS-AHL, furanone C-30, patulin, penicillic acid and 4-nitropyridine-N-oxide did not have any effect on protease activity, on gene expression or bean sprout appearance at nongrowth inhibitory concentrations.

Extracts from garlic and bean sprouts induced the QS system of Pectobacterium in bean sprouts and a broth system, respectively. Among the several well-known QSI compounds, only PenS-AHL and HepS-AHL, inhibited QS-regulated protease activity of Pectobacterium A2JM in broth cultures, but had no effect on bean sprout spoilage.

The QSI compounds must be selected in the specific system in which they are to function and they cannot easily be transferred from one QS system to another.