Proteomic Profiling of the Acid Stress Response in Lactobacillus plantarum 423

Acid tolerance is considered an important characteristic of probiotic bacteria. Lactobacillus plantarum 423 tolerates acidic pH and is the ideal candidate in which to study molecular mechanisms that acid-tolerant lactic acid bacteria employ to survive such conditions. In this study we recorded changes in the protein profile of L. plantarum 423 when exposed to pH 2.5 by using a gel-free nanoLC-MS/MS proteomics approach. In total, 97 proteins were detected as more abundant, and 12 proteins were detected solely when strain 423 was exposed to pH 2.5. General stress response proteins, the utilization of a variety of carbohydrate sources in a glucose rich environment, altered pyruvate metabolism, increased lysine biosynthesis, and a significant oxidative stress response was observed in acid-stressed cells. The accumulation of basic compounds also seemed to play an integral role in the response to acid stress. We observed a marked decrease in proteins involved in cell wall and phospholipid biosynthesis, transcription, translation, and cell division. The most abundant protein detected was an uncharacterized protein, JDM1_2142. Functional analysis revealed that this protein plays a role in survival during acid stress. Our results contribute to the growing body of knowledge on the molecular mechanisms employed by lactobacilli, in particular L. plantarum, to ensure survival in acidic conditions.