2.6. Spore counts
To determine the number of spores in gut contents, samples were suspended in 10 ml of phosphate-buffered saline at 65°c. Sterile glass beads were added, and the suspension was incubated at 65°c for 1 h with frequent vortexing until there was little remaining residual solid matter. Serial dilutions were then made with PBS, plated on DSM plates containing kanamycin and Ampicillin, and incubated at 37°C for 2 days. B. subtilis colonies of strain rVP28-bs-gfp were identified by their colony morphology. Spore counts were extrapolated for the total weight of gut contents collected.