42-6 |
|
A. E. YOUSEF and E. M. Horton. Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Ct., 110 Parker Food Science Bldg., Columbus, OH 43210-1007 Recently, quorum sensing has been suggested to play a role in regulation of stationary phase transition in some bacteria. As bacteria enter the stationary phase, they reach high cell densities, and therefore may produce signaling molecules to monitor the crowding and avoid starvation as well as environmental stresses. This cell-cell communication is not limited to quorum sensing. Although a great number of studies addressed growth-associated signaling, limited or no research has dealt with the consequences of cell-cell communication in food processing. Preliminary studies in our laboratories provide evidence of this phenomenon in altering cell resistance to processing. Listeria monocytogenes Scott-A (a barosensitive strain) and OSY-8578 (a barotolerant strain) were examined in our laboratory for inter-strain interactions during growth and pressure processing. Spontaneous, antibiotic-resistant, mutants of L. monocytogenes Scott-A and OSY-8578 were developed to aid in enumerating each strain separately when both were present in a mixed culture. The two antibiotic-resistant strains were grown singly or in mixed cultures, and stationary-phase cultures were pressurized at 300 MPa for 2-6 min. Survivors of each strain, in the single or mixed cultures, were enumerated on appropriate antibiotic-containing agar media. Results show that sensitivity of Scott A to pressure was not affected by the presence of OSY-8578. On the contrary, resistance of OSY-8578 to pressure diminished in the presence of the pressure-sensitive Scott-A. These results provide preliminary evidence of inter-strain communication that alters the pressure resistance of pathogens. The interaction during co-incubation, as demonstrated in these preliminary data, may be different than that among strains that are mixed together immediately before processing. These interactions may prove significant, particularly in light of the conventional practice of preparing a “cocktail” of different strains of Listeria for commercial validation studies.
Session 42, Control of quorum sensing signals and antimicrobial effects on foods
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |