KMID : 0880220140520100849
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Journal of Microbiology 2014 Volume.52 No. 10 p.849 ~ p.855
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¥òB affects biofilm formation under the dual stress conditions imposed by adding salt and low temperature in Listeria monocytogenes
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Lee Jin-Ju
Lee Gil-Ho Shin Ji-Hyun
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Abstract
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The food-borne pathogenic bacteria Listeria monocytogenes can form biofilms on various surfaces including food-processing equipment. Biofilms offer survival benefits to the organisms entrapped against environmental insults. Moreover, the ¥òB transcription factor of L. monocytogenes plays an important role in its survival under various stress conditions. In this study, we evaluated whether ¥òB contributes to biofilm formation when L. monocytogenes is grown under various temperatures and media. When the wild-type strain was grown under static biofilm culture below ambient temperature (15¡ÆC) for 72 h, the difference in viable cell number (in both planktonic and biofilm cells) between the wild-type and ¥ÄsigB mutant increased by adding NaCl to BHI broth (9% salt BHI > 6% salt BHI > BHI, w/v), and the specific activity of ¥â-galactosidase was highly induced in the wild-type strain grown in 6% salt containing BHI broth. Furthermore, we measured surface-adhered biofilm forming ability using the crystal violet staining method. The wild-type strain formed a four times larger biofilm than that of the ¥ÄsigB mutant in 6% salt-BHI medium at 15¡ÆC over a 72 h incubation and also showed the highest level of ¥â-galactosidase specific activity. However, both the wild-type and ¥ÄsigB mutant L. monocytogenes were defective for forming a biofilm in 9% salt-BHI medium at 15¡ÆC. Our results suggest that ¥òB plays an enhanced role in surface-adhered biofilm formation when L. monocytogenes encounters dual stress conditions, such as 6% NaCl and low temperature.
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KEYWORD
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Listeria monocytogenes, biofilm, ¥òB, low temperature, salt stress
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