Fig. 5: K. pneumoniae reduces Parasutterella from the gut in a T6SS-dependent manner.

For absolute quantification of bacterial levels, droplet digital PCR (ddPCR) was performed on DNA extracted from fecal pellets of mice 24 h pre-infection and days 2, 4, and 7 post-inoculation with the WT or the T6SS−/− strain (n = 4 for each group). A–D Parasutterella and Duncaniella were quantified from each sample and then adjusted to the K. pneumoniae shedding on each given day to account for potential effects from the reduced colonization levels of T6−/− infected mice. Pre-infection (day 0) sample was adjusted to the average K. pneumoniae shedding from the same mouse on days 2, 4, and 7 post-inoculation to serve as a baseline for comparison. A Parasutterella levels in the murine GI tract following inoculation with WT or T6−/−. B Change in Parasutterella levels between days 0 and 2. C Duncaniella levels in the murine GI tract following inoculation with WT or T6−/−. D Change in Duncaniella levels between days 0 and 2. A, C A two-tailed Friedman test followed by Dunn’s multiple comparison test was performed comparing days 0, 2, 4, and 7 for WT and for T6−/− samples. Boxes and whiskers indicate the median and the minimum to maximum values, respectively. Adjusted p values from left to right: A 0.0058, 0.0058, 0.0058, 0.0201, 0.7358, 0.364, C > 0.9999, 0.2441, >0.9999, 0.0201, 0.7358, 0.364. B, D Shown are the mean +/− SEM values at day 0 and 2 post-infection, the tables indicate the average of the slopes for the samples from each mouse from day 0 to 2 post-infection, along with the standard error. Two-tailed Mann-Whitney U tests were performed to determine the statistical difference between the slopes. *, p < 0.05; **, p < 0.01.