Fig. 4

Acid tolerance of vole intestinal Lactobacillus isolates. Lactobacilli were incubated for 2 h (a) and 4 h (b) at various pH levels (pH 1, pH 2, pH 3, and pH 7) in PBS. Subsequently, the bacteria were inoculated in MRS and growth was determined after 24 h by OD_600nm measurement. Results are shown for the 17 most acid-tolerant Lactobacillus isolates as percent growth relative to growth after incubation at pH 7 (set to 100 %). L. johnsonii ATCC 33200 (green data points) and L. rhamnosus GG (red data points) were included as reference strains. While all strains tolerated prolonged incubation at pH 3 well, the depicted 17 strains survived pH 2 and some even pH 1. The reference strains appear to be more acid tolerant at pH 1 than the prairie vole strains. Data points are mean values from three experiments with duplicate measurements