| Summary: | 碩士 === 國立中央大學 === 生命科學研究所 === 90 === Lactic acid bacteria (LAB) are commonly used as probiotics or starter cultures in the fermented foods. Among them, Lactobacillus reuteri is the only enterolactobacillus known to be indigenous in a broad spectrum of hosts. When lactic acid bacteria were eaten with food, the microorganisms suffer the stresses of acid and bile salts in stomach and in duodenum, respectively. To investigate the proteome of stress response from lactic acid bacteria under these two types of stress, the viability of the bacterium under different pH and bile salts concentration was studied. Treated with Men-Rogosa-sharp (MRS) (pH 2.0) medium for 2 hours, 48% of Lactobacillus reuteri ATCC23272 survived. The survival rate was 3.0% under 0.3% bile salts in MRS (pH 5.7) medium for 2 hours. The proteomes of L. reuteri ATCC23272 treated with pH 2.0 or 0.3% bile salts were analyzed by two-dimensional polyacrylamide gel electrophoresis (2-DE) and quantified by Commassie blue staining. The peptide mass fingerprints of induced proteins were identified by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry via searching the SWISS-PROT and TrEMBL databases. Comparing the protein patterns of cell extracts from MRS media, there are 11, 9, and 6 spots induced by pH 2.0, 0.3% bile salts and the combination of two conditions, respectively. In addition to s54 and sS involved in the regulation of transcription, protein involved in folding such as GroEL is induced by two types of stress. Nitrous oxide reductase (NosL) is also induced by two types of stress. The acid shock protein, ornithine carbamoyltransferase, ATPase a and b subunit are acid response proteins induced by acid only. And GroES, ClpB, alkyl hydroperoxide reductase (AhpC) and ATP-binding cassette (ABC) transporter are induced when L. reuteri is treated with bile salts. The induction of D-alanine-D-alanine ligase (Ddl) by bile salts indicates bile salts may damage bacterial cell wall.
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