title: σ(B) affects biofilm formation under the dual stress conditions imposed by adding salt and low temperature in Listeria monocytogenes.
abstract: 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 σ(B) transcription factor of L. monocytogenes plays an important role in its survival under various stress conditions. In this study, we evaluated whether σ(B) 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°C) for 72 h, the difference in viable cell number (in both planktonic and biofilm cells) between the wild-type and ΔsigB mutant increased by adding NaCl to BHI broth (9% salt BHI > 6% salt BHI > BHI, w/v), and the specific activity of β-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 ΔsigB mutant in 6% salt-BHI medium at 15°C over a 72 h incubation and also showed the highest level of β-galactosidase specific activity. However, both the wild-type and ΔsigB mutant L. monocytogenes were defective for forming a biofilm in 9% salt-BHI medium at 15°C. Our results suggest that σ(B) plays an enhanced role in surface-adhered biofilm formation when L. monocytogenes encounters dual stress conditions, such as 6% NaCl and low temperature.
authors.affiliation: Institute of Science and Technology, College of Science and Technology, Korea University, Sejong, 339-700, Republic of Korea.
authors.forename: Jin-Ju
authors.initials: JJ
authors.lastname: Lee
authors.forename: Gilho
authors.initials: G
authors.lastname: Lee
authors.forename: Ji-Hyun
authors.initials: JH
authors.lastname: Shin
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D003470:Culture Media / Q000737:chemistry; D017353:Gene Deletion; D008089:Listeria monocytogenes / Q000187:drug effects / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D012492:Salts / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D012492:Salts; C079011:SigB protein, Bacteria; D012808:Sigma Factor