Effects of flavonoids on the phage susceptibility of <i>Escherichia coli</i> and on the transcription of chaperone gene <i>dnaK</i>

In this study, the dnaK gene-deletion mutant strain of Escherichia coli BW25113 showed a higher susceptibility than the wild-type strain of E. coli BW25113 to phage S127BCL3. Flavonoids, myricetin and quercetin which had been reported to suppress the role of DnaK were tested to examine their effects on the phage susceptibility of E. coli BW25113. A 6-h pretreatment with 500 µmol/L myricetin or quercetin increased the phage susceptibility of E. coli BW25113. A similar result was observed in E. coli O157:H7. Real-time quantitative polymerase chain reaction (qPCR) was conducted to investigate the effects of flavonoids on the transcription of chaperone genes (dnaK, dnaJ, groEL, and grpE) in E. coli. Pretreatment of wild-type E. coli BW25113 with flavonoids decreased the transcription of chaperone genes. This is the first report demonstrating the enhancement of the phage susceptibility of both E. coli BW25113 and E. coli O157:H7 by flavonoids. The results of this study on the combined effects of flavonoids involved in foods and phages on E. coli provide scientific bases for development of a novel biocontrol method of foodborne bacteria.