(a) FACS dot plots of in situ conjugations using EcGT2 pGT-L3 donors in a cohort of mice from a different vendor (Charles River Laboratories). Green boxes define the sorted GFP+mCherry– transconjugant populations. Flow cytometry was performed 3 times, on fecal samples from individual cohoused mice, with similar results. (b) 16S taxonomic classification of FACS-enriched GFP+mCherry– transconjugants of pGT-L3 at 6 h post-gavage. Relative abundance of each OTU in the unsorted population is shown in the grayscale heat map, and fold enrichment for transconjugants of each OTU is shown in the orange heat map, with annotated taxonomic identities. Bracketed values indicate confidence of taxonomic assignment by RDP Classifier. Each column represents bacteria from one mouse. Genera with successfully cultivated isolates are denoted by stars. (c) Metagenomic 16S rRNA sequencing of mouse fecal samples shows that mice from different vendors have divergent gut microbiomes, with some shared OTUs. (d) In in situ experiments using the same vector library (pGT-L6) in cohorts of 3 mice each from different vendors, 10 transconjugant OTUs were shared between cohorts.