title: A single point mutation in the listerial betL σ(A)-dependent promoter leads to improved osmo- and chill-tolerance and a morphological shift at elevated osmolarity.
abstract: Betaine uptake in Listeria monocytogenes is mediated by three independent transport systems, the simplest of which in genetic terms is the secondary transporter BetL. Using a random mutagenesis approach, based on the E. coli XL1 Red mutator strain, we identified a single point mutation in a putative promoter region upstream of the BetL coding region which leads to a significant increase in betL transcript levels under osmo- and chill-stress conditions and a concomitant increase in stress tolerance. Furthermore, the mutation appears to counter the heretofore unreported "twisted" cell morphology observed for L. monocytogenes grown at elevated osmolarities in tryptone soy broth.
authors.affiliation: Alimentary Pharmabiotic Centre; University College Cork; Cork, Ireland; Department of Biological Sciences; Cork Institute of Technology; Cork, Ireland.
authors.forename: Roland F
authors.initials: RF
authors.lastname: Hoffmann
authors.affiliation: Alimentary Pharmabiotic Centre; University College Cork; Cork, Ireland.
authors.forename: Susan
authors.initials: S
authors.lastname: McLernon
authors.affiliation: Department of Biological Sciences; Cork Institute of Technology; Cork, Ireland.
authors.forename: Audrey
authors.initials: A
authors.lastname: Feeney
authors.affiliation: Alimentary Pharmabiotic Centre; University College Cork; Cork, Ireland.
authors.forename: Colin
authors.initials: C
authors.lastname: Hill
authors.affiliation: Alimentary Pharmabiotic Centre; University College Cork; Cork, Ireland; Department of Biological Sciences; Cork Institute of Technology; Cork, Ireland.
authors.forename: Roy D
authors.initials: RD
authors.lastname: Sleator
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001622:Betaine / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003080:Cold Temperature; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008089:Listeria monocytogenes / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D013312:Stress, Physiological
chemical_list: D001426:Bacterial Proteins; C119698:BetL protein, Listeria monocytogenes; D002352:Carrier Proteins; D004269:DNA, Bacterial; D001622:Betaine
keywords: Listeria; chill-tolerance; osmotolerance; salt stress; twisted cells