Fig. 6.

Spatial partitioning of G. apis and G. apicola in bee guts. Honey bees were colonized with Snodgrassella expressing E2-Crimson (magenta), G. apicola expressing red chromoprotein (yellow), or G. apis expressing green fluorescent protein (cyan) alone or in combination. After 7 d, we dissected bee guts and imaged them using fluorescent confocal microscopy. (A) Dissected gut of an adult honey bee, and schematic of gut regions. We compared the (i) pylorus and (ii) distal ileum-rectum junction for different samples (B–E). White boxes across A–E indicate the pyloric sphincter regions. (Scale bars: 100 µm in B–E.) (B) Uncolonized bees show minimal background fluorescence in pylorus and ileum. (C) Monocolonized G. apis (cyan) colonizes the pylorus, with minimal colonization of ileum (i-ii). (D) Cocolonization of G. apicola (yellow) and Snodgrassella (magenta) show slight pylorus colonization and robust ileum colonization. (E) Bees coinoculated with G. apis (cyan), G. apicola (yellow), and Snodgrassella (magenta). Cocolonized species retain similar localization to monoculture strains, with G. apis outcompeting G. apicola at the pylorus. For each inoculation condition, 6 to 12 bees were inspected during each of three independent colonization trials. Representative images are shown. (F) Ratio of ureC gene copies between pylorus and distal ileum in 15 age-controlled bees with a conventional gut microbiome. ureC gene copy number was normalized based on 16S rRNA gene copy number. Samples with ratio above 1 (red dotted line) have higher abundance of G. apis in pylorus than in ileum (Wilcoxon signed-rank test P = 0.012).