Fig. 4

Sugars and buffers have a synergistic effect on expression and secretion titer. a Relative bulk secretion titer of SptP-DH-2xFLAG-6xHis secreted in media containing 10 g/L tryptone, 5 g/L yeast extract, and the additives listed in Additional file 1: Table S7. Bulk secretion titer was normalized to LB-L with no additives (dotted line) using semi-quantitative western blotting. Statistical significance was determined by Welch’s unequal variances t-test. Significance denoted by “**” represents p < 0.01, and “*” represents p < 0.05. b Relative bulk secretion titer versus relative bulk expression. All error bars represent standard error for three biological replicates