Browsing by Subject "Listeria monocytogenes"

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Adaptation of Listeria monocytogenes to perturbation of c‐di‐AMP metabolism underpins its role in osmoadaptation and identifies a fosfomycin uptake system
(2022) Wang, Mengyi; Wamp, Sabrina; Gibhardt, Johannes; Holland, Gudrun; Schwedt, Inge; Schmidtke, Kai‐Uwe; Scheibner, Katrin; Halbedel, Sven; Commichau, Fabian M.
The human pathogen Listeria monocytogenes synthesizes and degrades c‐di‐AMP using the diadenylate cyclase CdaA and the phosphodiesterases PdeA and PgpH respectively. c‐di‐AMP is essential because it prevents the uncontrolled uptake of osmolytes. Here, we studied the phenotypes of cdaA, pdeA, pgpH and pdeA pgpH mutants with defects in c‐di‐AMP metabolism and characterized suppressor mutants restoring their growth defects. The characterization of the pdeA pgpH mutant revealed that the bacteria show growth defects in defined medium, a phenotype that is invariably suppressed by mutations in cdaA. The previously reported growth defect of the cdaA mutant in rich medium is suppressed by mutations that osmotically stabilize the c‐di‐AMP‐free strain. We also found that the cdaA mutant has an increased sensitivity against isoleucine. The isoleucine‐dependent growth inhibition of the cdaA mutant is suppressed by codY mutations that likely reduce the DNA‐binding activity of encoded CodY variants. Moreover, the characterization of the cdaA suppressor mutants revealed that the Opp oligopeptide transport system is involved in the uptake of the antibiotic fosfomycin. In conclusion, the suppressor analysis corroborates a key function of c‐di‐AMP in controlling osmolyte homeostasis in L. monocytogenes.
Improving food safety of sprouts and cold-smoked salmon by physical and biological preservation methods
(2007) Weiss, Alexander; Hammes, Walter
The safety of raw, ready-to-eat foods is of paramount importance and is in the focus of the food industry, consumers as well as food scientists. To improve the food safety status of the products, efficient decontamination as an important processing step and/or the use of protective microorganisms as biocontrol agents are promising approaches. In our work we successfully used these approaches for raw sprouts and cold-smoked salmon as examples for RTE foods. Therefore the set goals have been successfully performed and essential scientific knowledge has been contributed. The results have been published and are described in the following in form of the respective abstracts. Thermal seed treatment to improve the food safety status of sprouts: Alexander Weiss and Walter P. Hammes. 2003. Thermal seed treatment to improve the food safety status of sprouts. (Journal of Applied Botany. 77: 152-155) Efficacy of heat treatment in the reduction of salmonellae and Escherichia coli O157:H? on alfalfa, mung bean and radish seeds used for sprout production: Weiss Alexander and Hammes, Walter P. 2005. Efficacy of heat treatment in the reduction of salmonellae and Escherichia coli O157:H? on alfalfa, mung bean and radish seeds used for sprout production. (Eur. Food Res. Tech. 211, 187-191) Characterization of the microbiota of sprouts and their potential for application as protective cultures: Alexander Weiss, Christian Hertel, Silke Grothe, Diep Ha and Walter P. Hammes 2006. Characterization of the microbiota of sprouts and their potential for application as protective cultures. (Applied and Environmental Microbiology. Submitted for publication) Lactic acid bacteria as protective cultures against Listeria spp.on cold-smoked salmon: Weiss Alexander and Hammes, Walter P. 2006. Lactic acid bacteria as protective cultures against Listeria spp.on cold-smoked salmon. (Eur. Food Res. Tech. 222, 343-346)