title: Diversity of acid stress resistant variants of Listeria monocytogenes and the potential role of ribosomal protein S21 encoded by rpsU.
abstract: The dynamic response of microorganisms to environmental conditions depends on the behavior of individual cells within the population. Adverse environments can select for stable stress resistant subpopulations. In this study, we aimed to get more insight in the diversity within Listeria monocytogenes LO28 populations, and the genetic basis for the increased resistance of stable resistant fractions isolated after acid exposure. Phenotypic cluster analysis of 23 variants resulted in three clusters and four individual variants and revealed multiple-stress resistance, with both unique and overlapping features related to stress resistance, growth, motility, biofilm formation, and virulence indicators. A higher glutamate decarboxylase activity correlated with increased acid resistance. Whole genome sequencing revealed mutations in rpsU, encoding ribosomal protein S21 in the largest phenotypic cluster, while mutations in ctsR, which were previously shown to be responsible for increased resistance of heat and high hydrostatic pressure resistant variants, were not found in the acid resistant variants. This underlined that large population diversity exists within one L. monocytogenes strain and that different adverse conditions drive selection for different variants. The finding that acid stress selects for rpsU variants provides potential insights in the mechanisms underlying population diversity of L. monocytogenes.
authors.affiliation: Top Institute Food and Nutrition Wageningen, Netherlands ; Laboratory of Food Microbiology, Wageningen University Wageningen, Netherlands.
authors.forename: Karin I
authors.initials: KI
authors.lastname: Metselaar
authors.affiliation: Laboratory of Food Microbiology, Wageningen University Wageningen, Netherlands.
authors.forename: Heidy M W
authors.initials: HM
authors.lastname: den Besten
authors.affiliation: Top Institute Food and Nutrition Wageningen, Netherlands ; NIZO Food Research Ede, Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Boekhorst
authors.affiliation: Top Institute Food and Nutrition Wageningen, Netherlands ; NIZO Food Research Ede, Netherlands ; Bacterial Genomics Group, CMBI Centre for Molecular and Biomolecular Informatics, Radboud University Medical Center Nijmegen, Netherlands.
authors.forename: Sacha A F T
authors.initials: SA
authors.lastname: van Hijum
authors.affiliation: Top Institute Food and Nutrition Wageningen, Netherlands ; Laboratory of Food Microbiology, Wageningen University Wageningen, Netherlands.
authors.forename: Marcel H
authors.initials: MH
authors.lastname: Zwietering
authors.affiliation: Top Institute Food and Nutrition Wageningen, Netherlands ; Laboratory of Food Microbiology, Wageningen University Wageningen, Netherlands.
authors.forename: Tjakko
authors.initials: T
authors.lastname: Abee
keywords: SNP analysis; glutamate decarboxylase; heterogeneity; phenotypic characterization; trade-off; whole genome sequencing