29G-7 |
Extracellular protectants secreted by Clostridium perfringens cells at elevated temperatures |
N. HEREDIA, Departmento of Microbiologia e Inmunologia, Universidad A. de Nuevo Leon, Fac. C. Biologicas, Apdo. Postal 124-F, San Nicolas, NL, 66451, Mexico, S. Garcia, Departmento de Micobiologia, Universidad de Nuevo Leon, Facultad de Ciencias Biologicas, Apdo Postal 124-F, San Nicolas, NL, 66451, Mexico, and P. Ybarra, Departmento de Microbiologia, Universidad de Nuevo Leon, Fac. C. Biologicas, Apdo. Postal 124-F, San Nicolas, NL, 66451. Justification: Several reports have shown that at supraoptimal temperatures E. coli cultures accumulate extracelullar protective metabolites that promote the adaptation of this bacterium to unfavorable conditions. It is known that Clostridium perfringens adapts to high temperatures after a heat shock, however, no information is available about the involvement of supernatant metabolites in this response. Objective: In this work, we demonstrated the ability of C. perfringens to adapt to high temperatures by means of an extracellular factor that was released to the culture medium or food after a heat shock. Methods: Cells were grown in 4 ml fluid thioglycollate medium or chicken broth and incubated at 37°C. When cells reached mid-log phase, they were heat shocked at 50°C for 30 min. After that, cultures were centifugated and supernatants were transferred to non-shocked cells. Heat tolerance of these cells was performed at 55°C. Viable cells were determined by plate count at different times. In some cases, 100 ml trypsin (1:250) were added to the supernatants and incubated at 37°C for 30 min or the supernatants were heated at 65° or 100°C for 15 min. The supernatant was fractioned using Nanosep 10 K and low pressure liquid chromatography. PAGE was made of fractions showing heat-protective activity. Results: Results indicated that a heat shock applied to C. perfringens cells released compounds to the medium that conferred heat-tolerance to non-shocked cells in culture media and in chicken broth. The heat-protective activity was lost if the supernatant was treated with heat or trypsin. PAGE and Western blot analysis of the supernatant fraction with heat-protective activity indicated the presence of a 57kDa protein that cross reacted with GroEl antiserum. Significance: The mechanisms that confer adaptation of this bacterium to heat may be an important aspect of food safety because of the widespread application of thermal processing to the control of pathogenic microorganisms.
Session 29G, Food Microbiology: General
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