29G-13 |
Negative regulation of LepA in Listeria monocytogenes survival and growth in stress conditions |
K. P. KIM, T. Geng, and A. K. Bhunia. Dept. of Food Science, Purdue Univ., 745 Agriculture Mall Dr., West Lafayette, IN 47907-2009 Listeria monocytogenes is a food-borne pathogen, ubiquitous in the environment and resistant to many stress conditions such as temperature (0~50oC), pH (4.3~9.6) and salt. In this study, we examined the involvement of LepA protein, presumably a GTP binding protein, for the organism¢s survival and growth in various stress conditions. In a previous study, we showed increased LepA expression with increasing temperatures. The objectives of this study were to investigate the role of LepA in L. mococytogenes growth and survival under various stressful conditions encountered by the organism during processing, storage or infection process. In-frame lepA deletion mutant was constructed using splicing by overlap extension method. To monitor survival, mutant and wild type (WT) strains were treated with acidic pH (3.0), ethanol (15%) and high temperature (55oC) while to determine the growth, the bacteria were incubated in media containing hydrogen peroxide (65 mM), salt (3, 5 and 8% of NaCl) or held at different temperatures (4, 37 and 45oC). Interestingly lepA mutant showed higher survival rate than that of WT in most of the stressful environments. After 90 min of incubation at low pH (3.0) or high temperature (55oC), there was approximately one log difference between WT and mutant. No differences were observed in ethanol treatment. Both strains showed similar growth curve when grown in the presence of different concentration of salts or hydrogen peroxide. However, at 4oC, mutant showed shorter lag phase than that of WT. These data indicated that LepA in L. monocytogenes is important regulatory factor for organism¢s survival and growth in various unfavorable environments. Although physiological role of LepA is still not clear, data indicate that it possibly regulates factors that help bacteria to cope in stressful envirionments.
Session 29G, Food Microbiology: General
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