"After 3 weeks of tannin diets the proportion of tannin-resistant bacteria increased significantly (P < 0.05) from 0.3% ± 5.5% to 25.3% ± 8.3% with a 0.7% tannin diet and to 47.2% ± 5.1% with a 2% tannin diet. The proportion of tannin-resistant bacteria returned to preexposure levels in the absence of dietary tannins."
"tannins selected for Enterobacteriaceae and Bacteroides species. ... there was a corresponding decrease in the gram-positive Clostridium leptum group and other groups."So we've covered before that a happy biome may require a consistent fiber amount, and a consistent amount of FODMAPs, but we may also want to watch our tannins consistency. Tannins are found in all sorts of plant foods, but our biggest sources are generally our beverages, especially coffee, tea, and wine, but also in many fruit juices.
Bacteriodes are often included in probiotics. Advanced Orthomolecular Research Probiotic 3 includes a different Clostridium species, but Clostridium leptum is associated with inflammatory bowel disease. Enterobacteriaceae are a mixed bag of friendly and non-friendly bacterium.
I don't think there's any evidence yet that the tannin-resistant bacteria are better or worse for you, but if you're happy with your microbiome you might consider the consistency of your favorite brew as a part of your health maintenance plan. If you're not happy with your microbiome, a shift up or down in tannins might be considered. At the very least a temporary shift and return to normal may shake things up a bit and give your new probiotic a competitive advantage over the natives.
Now, back to my cup of tea...