100A-4 |
Increased transcription of lepA homologue, a GTP binding protein, in Listeria monocytogenes during heat stress |
K. P. KIM1, T. Geng, F. Soyer, and A. K. Bhunia. (1) Department of Food Science, Purdue University, 1160 Food Science Building, West Lafayette, IN 47907 Listeria monocytogenes is an opportunistic food-borne pathogen capable of enduring a variety of hostile conditions such as high and low temperatures, acids, salts and antimicrobial agents. Identification and characterization of stress related proteins will promise our understanding of its unusual abilities. In this study, differential expression of lepA homologue, a GTP binding protein, during growth at 37 oC and 42 oC was investigated. To examine its role in stress response, Listeria monocytogenes strain, F4244 (serotype 4b), was challenged with elevated temperature and transcriptional as well as translational level of lepA was investigated by carrying out RT-PCR, Northern blotting and immunobloting. In RT-PCR, total mRNAs, isolated from exponentially growing Listeria at 37 oC and 42 oC, were used and the result demonstrated an increased amplification of lepA-specific fragment at 42 oC than 37 oC. In Western blot analysis using rabbit anti-LepA polyclonal antibody showed that LepA protein expression has increased at 42 oC. To further evaluate these observations, we varied the incubation time (1, 2, 3, 4 and 9 hours at 42 oC) and Northern hybridization was performed using lepA probe. The result showed that the lepA transcription was increased several folds after 9 hours incubation at 42 oC, consistent with RT-PCR and Western blot results.However, mRNA transcripts decreased right after temperature increase from 37 oC to 42 oC. Furthermore, the size of lepA transcript was figured out to be approximately 1.9 kb which is about the size of lepA in L. monocytogenes EGD (serotype 1/2a). These data indicate, lepA is a potential stress response protein with enhanced expression at 42 oC and possibly helps L. monocytogenes to survive under heat stress condition.
Session 100A, Food Microbiology: General II
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