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Description:
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Cell -to -cell communication , termed quorum sensing , mediated by AI -2 like
activity , has been reported to regulate the expression of a variety of genes in E . coli
O157 :H7 . A previous study in our laboratory has shown that foods can contain
compounds that can interfere with AI -2 signaling . The underlying hypothesis of our
studies is that the autoinducer molecules such as AI -2 are involved in the virulence and
survival of enteric bacterial pathogens on food and food ingredients . The influence of
AI -2 like activity on the survival and expression of virulence genes (hha and yadK ) in
E .coli O157 :H7 was studied when the organism was stored in different types of ground
beef extracts such as : cooked , uncooked , and autoclaved . The survival was observed at
refrigeration temperature , while change in gene expression was studied using real -time
PCR . Higher survival was observed in the cell exposed to cell free supernatant (CFS )
containing AI -2 like molecules , compared to the one which was exposed to heat
degraded AI -2 like molecules . The survival of cells was higher when exposed to cooked
ground beef extracts compared to uncooked and autoclaved ground beef extracts .
Similarly , higher gene expressions of both hha and yadK genes were observed in cells
that were exposed to cooked beef extract samples as compared to samples that wereuncooked or autoclaved . About a 2 fold higher gene expression for both hha and yadK
gene was observed when cells were subjected to cooked ground beef extracts in the
presence of AI -2 like molecules compared to the ones exposed to uncooked ground beef
extracts in the presence of AI -2 like molecules . Likewise , 3 -fold higher gene expression
was observed for cells exposed to cooked ground beef extracts compare to autoclaved
ground beef extracts in the presence of AI -2 like molecules . The results suggest that the
survival and virulence of enteric bacterial pathogens such as E .coli O157 :H7 can be
influenced by the interaction of food components and autoinducers such as AI -2 , that are
involved in bacterial cell communications . |