Molecular analysis of the role of osmolyte transporters opuCA and betL in Listeria monocytogenes after cold and freezing stress.
Listeria monocytogenes is a food-borne pathogen of humans and other animals. The striking ability to survive several stresses usually used for food preservation makes L. monocytogenes one of the biggest concerns to the food industry. This ubiquity can be partly explained by the ability of the organism to grow and persist at very low temperatures, a consequence of its ability to accumulate cryoprotective compound called osmolytes. A quantitative RT-PCR assay was used to measure mRNA transcript accumulation for the stress response genes opuCA and betL (encoding carnitine and betaine transporters, respectively) and the housekeeping gene 16S rRNA. Assays were conducted on mid-exponential phase L. monocytogenes cells exposed to conditions reflecting cold and freezing stress, conditions usually used to preserve foods. We showed that expression of the two cold-adapted genes encoded the transporters of the cryoprotectants carnitine and betaine in ATCC 19115 and the food-isolated L. monocytogenes S1 is induced after cold and freezing stress exposure. Furthermore, transcriptional analysis of the genes encoding opuCA and betL revealed that each transporter is induced to different degrees upon cold shock of L. monocytogenes ATCC 19115 and S1. Our results confirm an increase in carnitine uptake at low temperatures more than in betaine after cold-shocked temperature compared to the non-stress control treatment. It was concluded the use of carnitine and betaine as cryoprotectants is essential for rapid induction of the tested stress response under conditions typically encountered during food preservation.
Laboratory of Analysis, Treatment and Valorisation of Environment Pollutants and Products, Faculty of Pharmacy, Monastir University, 5000, Monastir, Tunisia. miladi_h@yahoo.fr.
Hanene
H
Miladi
Laboratory of Analysis, Treatment and Valorisation of Environment Pollutants and Products, Faculty of Pharmacy, Monastir University, 5000, Monastir, Tunisia.
Hamouda
H
Elabed
Laboratory of Analysis, Treatment and Valorisation of Environment Pollutants and Products, Faculty of Pharmacy, Monastir University, 5000, Monastir, Tunisia.
Rihab
R
Ben Slama
Regional Laboratory of Public Health of Monastir, Monastir, Tunisia.
Amel
A
Rhim
Laboratory of Analysis, Treatment and Valorisation of Environment Pollutants and Products, Faculty of Pharmacy, Monastir University, 5000, Monastir, Tunisia.
Amina
A
Bakhrouf
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001622:Betaine / Q000378:metabolism; D002331:Carnitine / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003080:Cold Temperature; D058639:Cold-Shock Response; D005615:Freezing; D050485:GABA Plasma Membrane Transport Proteins; D015964:Gene Expression Regulation, Bacterial; D008089:Listeria monocytogenes / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; C119698:BetL protein, Listeria monocytogenes; D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; C072207:betaine plasma membrane transport proteins; D001622:Betaine; D002331:Carnitine
Cold stress; Listeria monocytogenes; Quantitative RT-PCR; opuCA and betL