Susceptibility and Adaptive Response to Bile Salts in Propionibacterium freudenreichii : Physiological and Proteomic Analysis

Abstract

Tolerance to digestive stresses is one of the main factors limiting the use of microorganisms as live probiotic agents. Susceptibility to bile salts and tolerance acquisition in the probiotic strain Propionibacterium freudenreichii SI41 were characterized. We showed that pretreatment with a moderate concentration of bile salts (0.2 g/liter) greatly increased its survival during a subsequent lethal challenge (1.0 g/liter, 60 s). Bile salts challenge led to drastic morphological changes, consistent with intracellular material leakage, for nonadapted cells but not for preexposed ones. Moreover, the physiological state of the cells during lethal treatment played an important role in the response to bile salts, as stationary-phase bacteria appeared much less sensitive than exponentially growing cells. Either thermal or detergent pretreatment conferred significantly increased protection toward bile salts challenge. In contrast, some other heterologous pretreatments (hypothermic and hyperosmotic) had no effect on tolerance to bile salts, while acid pretreatment even might have sensitized the cells. Two-dimensional electrophoresis experiments revealed that at least 24 proteins were induced during bile salts adaptation. Identification of these polypeptides suggested that the bile salts stress response involves signal sensing and transduction, a general stress response (also triggered by thermal denaturation, oxidative toxicity, and DNA damage), and an alternative sigma factor. Taken together, our results provide new insights into the tolerance of P. freudenreichii to bile salts, which must be taken into consideration for the use of probiotic strains and the improvement of technological processes.

Proteomic Analysis of Global Changes in Protein Expression during Bile Salt Exposure of Bifidobacterium longum NCIMB 8809

“…Induction of dnaK at the transcriptional level was shown in Bifidobacterium adolescentis following heat, salt, and bile treatments (49). DnaK was induced in Propionibacterium freudenreichii, a microorganism closely related to bifidobacteria, as a response to bile, acid, and heat (32,33) and in B. breve as a response to osmotic shock (58). GroEL clearly responds to acid stress in P. freudenreichii (33) and Streptococcus oralis (61).…”

Dairy Propionibacteria: Less Conventional Probiotics to Improve the Human and Animal Health

“…Furthermore, acid pretreatment sensitized cells to bile salts challenge and vice versa. Heat and acid responses did not present significant cross-protection and no cross-protection of salt-adapted cells against heat stress was observed for these propionibacteria [48][49][50].…”

“…Many studies have demonstrated by in vitro assays the ability of dairy propionibacteria to survive and tolerate the gastrointestinal conditions [130][131][132][133][134]. This tolerance could be improved by a pre-adaptation of the microorganisms to the adverse conditions of the gut by a brief exposure to the stressful conditions at a non-lethal level [48,135].…”

“…The stress adaptation proteins were particularly investigated in P. freudenreichii and its genome, finding out that they are differentially expressed depending on the strain and the stress [40,[48][49][50]. Acid and bile stresses, induce the synthesis of the following proteins: pyruvate-flavodoxin oxidoreductase and succinate dehydrogenase which are involved in electron transport and ATP synthesis, as well as glutamate decarboxylase and aspartate ammonia-lyase, which are involved in intracellular pH homeostasis.…”

Cellular injuries on spray‐dried Lactobacillus rhamnosus GG and its stability during food storage

“…Cells were examined and photographed with S-2700 Scanning Electron Microscope (HITACHI) operating at 20 kV. Micrographs were taken at various magnifications (Leverrier et al, 2003).…”