Fig. 1. Snodgrassella strains protect against N. ceranae via the ROS-associated immune response in the honeybee gut.

a Schematic illustration of experimental design. Microbiota-free (MF) bees were colonized with B. choladohabitans W8113, B. mellis W8089, L. apis W8172, G. apicola B14384H2, and S. alvi M0351 for 7 days and then orally infected with N. ceranae. See also Supplementary Fig. 1. b Absolute abundance of N. ceranae spores in the midgut 10 days post-infection with N. ceranae. n = 10 bees from two cup cages. The pairwise difference between the MF group and each mono-colonization group was tested by the two-sided Mann–Whitney U test. c, d The expression level of the Duox and Nox genes in the midgut following S. alvi M0351 colonization (n = 5 bees for both groups). Two-sided Mann–Whitney U test. e Fluorescence staining for Reactive oxygen species (ROS) signal (Red) within the midgut cells of MF and mono-colonized bees with S. alvi. Honeybee gut stained using 4′,6-diamidino-2-phenylindole (DAPI; blue). f H₂O₂ concentration in the midgut of MF and mono-colonized bees with S. alvi (n = 3 bees for both groups). Scale bars = 250 μm. Multiple two-tailed t-tests. Error bars represent mean SD. Source data are provided as a Source Data file.