title: Starvation induces physiological changes that act on the cryotolerance of Lactobacillus acidophilus RD758.
abstract: The relationship between lactose starvation and cryotolerance was investigated in Lactobacillus acidophilus RD758. Cryotolerance was measured from the acidification activity of cells recovered after 18-h lactose starvation. It was compared to that of nonstarved cells, both of them in a stationary phase and in the same medium. This measurement allowed quantifying the initial acidification activity before freezing, as well as the loss of acidification activity during freezing and the rate of loss during frozen storage. Even if initial acidification activity was similar for nonstarved and starved bacteria, the latter displayed a significantly better resistance to freezing and frozen storage at -20°C. To investigate the mechanisms that triggered these cryotolerance phenomena, the membrane fatty acid composition was determined by gas chromatography, and the proteome was established by 2-D electrophoresis, for starved and nonstarved cells. The main outcome was that the improved cryotolerance of starved cells was ascribed to two types of physiological responses as a result of starvation. The first one corresponded to an increased synthesis of unsaturated, cyclic, and branched fatty acids, to the detriment of saturated fatty acids, thus corresponding to enhanced membrane fluidity. The second response concerned the upregulation of proteins involved in carbohydrate and energy metabolisms and in pH homeostasis, allowing the cells to be better prepared for counteracting the stress they encountered during subsequent cold stress. These two phenomena led to a cross-protection phenomenon, which allowed better cryotolerance of Lb. acidophilus RD758, following cellular adaptation by starvation.
authors.affiliation: AgroParisTech INRA, UMR 782 Génie et Microbiologie des Procédés Alimentaires, Thiverval-Grignon 78850, France.
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Jérôme
authors.initials: J
authors.lastname: Delettre
authors.forename: Georges
authors.initials: G
authors.lastname: Corrieu
authors.forename: Catherine
authors.initials: C
authors.lastname: Béal
mesh_terms: D000143:Acids; D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D058639:Cold-Shock Response; D015925:Cryopreservation / Q000379:methods*; D005227:Fatty Acids / Q000032:analysis; D005615:Freezing; D007779:Lactobacillus acidophilus / Q000166:cytology / Q000502:physiology*; D008560:Membrane Fluidity; D020543:Proteome / Q000032:analysis; D013217:Starvation
chemical_list: D000143:Acids; D001426:Bacterial Proteins; D005227:Fatty Acids; D020543:Proteome