New convenient defined media for [(35)S]methionine labelling and proteomic analyses of probiotic lactobacilli

AIMS: To develop experimental conditions for efficient protein radiolabelling and two-dimensional (2D) polyacrylamide gel electrophoresis for investigation of stress proteomes of probiotic Lactobacillus spp. METHODS AND RESULTS: Three chemically defined media (CDM) optimized from a commercial medium supported rapid growth of the probiotic Lactobacillus rhamnosus E97800, Lactobacillus brevis ATCC 8287 and Lactobacillus reuteri E97849, and a broad range of other lactic acid bacteria. These CDM allowed efficient protein radiolabelling, requiring as little as 200 mul of logarithmic culture and pulse-chase labelling of 20 min to detect c. 300 distinct protein spots in a mini-scale 2D-gel. Proteins including DnaK, GroEL and ClpATPases were identified from the 2D-gels by immunoblotting. CONCLUSIONS: Radiolabelling coupled with 2D gel electrophoresis provides a sensitive means to monitor changes in protein synthesis rates in probistic lactobacilli. SIGNIFICANCE AND IMPACT OF THE STUDY: Efficient tools for proteomic analyses of probiotic Lactobacillus were developed and applied for stress-response studies.