title: Analysis of strains lacking known osmolyte accumulation mechanisms reveals contributions of osmolytes and transporters to protection against abiotic stress.
abstract: Osmolyte accumulation and release can protect cells from abiotic stresses. In Escherichia coli, known mechanisms mediate osmotic stress-induced accumulation of K(+) glutamate, trehalose, or zwitterions like glycine betaine. Previous observations suggested that additional osmolyte accumulation mechanisms (OAMs) exist and their impacts may be abiotic stress specific. Derivatives of the uropathogenic strain CFT073 and the laboratory strain MG1655 lacking known OAMs were created. CFT073 grew without osmoprotectants in minimal medium with up to 0.9 M NaCl. CFT073 and its OAM-deficient derivative grew equally well in high- and low-osmolality urine pools. Urine-grown bacteria did not accumulate large amounts of known or novel osmolytes. Thus, CFT073 showed unusual osmotolerance and did not require osmolyte accumulation to grow in urine. Yeast extract and brain heart infusion stimulated growth of the OAM-deficient MG1655 derivative at high salinity. Neither known nor putative osmoprotectants did so. Glutamate and glutamine accumulated after growth with either organic mixture, and no novel osmolytes were detected. MG1655 derivatives retaining individual OAMs were created. Their abilities to mediate osmoprotection were compared at 15°C, 37°C without or with urea, and 42°C. Stress protection was not OAM specific, and variations in osmoprotectant effectiveness were similar under all conditions. Glycine betaine and dimethylsulfoniopropionate (DMSP) were the most effective. Trimethylamine-N-oxide (TMAO) was a weak osmoprotectant and a particularly effective urea protectant. The effectiveness of glycine betaine, TMAO, and proline as osmoprotectants correlated with their preferential exclusion from protein surfaces, not with their propensity to prevent protein denaturation. Thus, their effectiveness as stress protectants correlated with their ability to rehydrate the cytoplasm.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Murdock
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Tangi
authors.initials: T
authors.lastname: Burke
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Chelsea
authors.initials: C
authors.lastname: Coumoundouros
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Doreen E
authors.initials: DE
authors.lastname: Culham
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada School of Mathematical and Natural Sciences, Arizona State University at the West Campus, Phoenix, Arizona, USA.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Deutch
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: James
authors.initials: J
authors.lastname: Ellinger
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Craig H
authors.initials: CH
authors.lastname: Kerr
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Plater
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: To
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
authors.forename: Geordie
authors.initials: G
authors.lastname: Wright
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada jwood@uoguelph.ca.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Wood
mesh_terms: D001622:Betaine / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology*; D008744:Methylamines / Q000378:metabolism; D009997:Osmotic Pressure; D011392:Proline / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D013312:Stress, Physiological; D013452:Sulfonium Compounds / Q000378:metabolism; D013696:Temperature; D014508:Urea / Q000378:metabolism
chemical_list: D003470:Culture Media; D008744:Methylamines; D013452:Sulfonium Compounds; D001622:Betaine; D012965:Sodium Chloride; D014508:Urea; D011392:Proline; C068078:dimethylpropiothetin; C005855:trimethyloxamine