Prolonged heat stress of Lactobacillus paracasei GCRL163 improves binding to human colorectal adenocarcinoma HT-29 cells and modulates the relative abundance of secreted and cell-surface located proteins

Lactobacillus casei group bacteria improve cheese ripening and may interact with host intestinal cells as probiotics, where surface proteins play a key role. Three complementary methods (trypsin shaving [TS], LiCl-sucrose extraction [LS] and extracellular culture fluid [ECF] precipitation) were used to analyze cell-surface proteins of L. paracasei GCRL163 by label-free quantitative proteomics after culture to mid-exponential phase in bioreactors at pH 6.5 and temperatures of 30oC to 45oC. A total of 416 proteins, including 300 with transmembrane, cell-wall anchoring and secretory motifs, and 116 cytoplasmic proteins were quantified as surface proteins. Although LS caused significantly greater cell lysis as growth temperature increased, higher numbers of extra-cytoplasmic proteins were exclusively obtained by LS treatment. Together with increased positive surface charge of cells cultured at supra-optimal temperatures, proteins including cell wall hydrolases Msp1/p75 and Msp2/p40, α-fucosidase AlfB, SecA an...