Abstract
Weak acid resistance limits the application of Bifidobacteria as a probiotic in food. The acid tolerance response (ATR), caused by pre-stressing cells at a sublethal pH, could improve the acid resistance of Bifidobacteria to subsequent acid stress. In this study, we used Bifidobacterium longum sub. longum BBMN68 to investigate the effect of the ATR on the acid stress response (ASR), and compared the difference between the ATR and the ASR by analyzing the two-dimensional-PAGE protein profiles and performing physiological tests. The results revealed that a greater abundance of proteins involved in carbohydrate metabolism and protein protection was present after the ASR than after the ATR in Bifidobacterium. Pre-stressing cells increased the abundance of proteins involved in energy production, amino acid metabolism, and peptidoglycan synthesis during the ASR of Bifidobacterium. Moreover, after the ASR, the content of ATP, NH3, thiols, and peptidoglycan, the activity of H+-ATPase, and the maintenance of the intracellular pH in the pre-stressed Bifidobacterium cells was significantly higher than in the uninduced cells. These results provide the first explanation as to why the resistance of Bifidobacterium to acid stress improved after pre-stressing.
Highlights
Several species in the genus Bifidobacterium are considered to be probiotic [1]
We discovered that pre- stressing increased the abundance of proteins involved in energy production, amino acid metabolism, and peptidoglycan synthesis during the acid stress response (ASR) of B.longumBBMN68
A previous study suggested that pre-stressing at pH 4.5 for 2 h could increase the survival of B. longumBBMN68 at pH 3.5 by 60-fold [5]
Summary
Several species in the genus Bifidobacterium are considered to be probiotic [1]. This has led to their widespread application in probiotic products. The acid resistance of Bifidobacterium is generally weak. Acid stress represents a major challenge to this organism, reducing viability and its putative probiotic effects [2, 3]. Strengthening acid tolerance is critical to enhance the survival of Bifidobacterium, and to ensure the quality and functionality of probiotic products.
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