For the first two it is quite clear that the antibiotic and diet affect the microbiome of the individuals. These changes cause metabolites or even direct action of the microbes on the rectal tissue which can result in the mutagenic affects.

Thanks Robert John Wolff for sharing. Regarding diet are you specifically referring to fiber in the diet or diet in general? I have not studied much on the topic of rectal tissue microbiota specifically and how rectal tissue microbiota is affected by diet and antibiotic changes--mostly the intestinal microbiota overall.

https://www.gutmicrobiotaforhealth.com/en/about-gut-microbiota-info/

Fiber is very important, and probably multiple types for the best microbial diversity (and it probably also has other effects on the intestinal lining). But other dietary components do make a difference, including sugars and alcoholic sugars (ie. sorbitol). Each food component either encourages the growth of some of the microbial constituents or may inhibit some, but the composition is constantly in flux especially with our varied diets (different diet each day).

Thanks for the link, it is interesting.

Robert John Wolff Yes! Thanks for sharing. I wonder if a diet high in sugar *and* low in fiber exacerbates the problem of bacteria eating at the mucosal lining (starving) or how high sugar intake affects the bacterial populations. What are your thoughts?

+Gut bacteria eat at mucus lining when no fiber in diet:

"And the four bacteria strains that flourished most in low-fiber and no-fiber conditions were the only ones that make enzymes that are capable of breaking down the long molecules called glycoproteins that make up the mucus layer. "

https://www.uofmhealth.org/news/archive/201611/high-fiber-diet-keeps-gut-microbes-eating-colon%E2%80%99s-lining

+Gut bacteria influence our cravings:

https://www.scientificamerican.com/article/how-gut-bacteria-tell-their-hosts-what-to-eat/

Sarah Fischbuch The two articles you cite are good. I believe you are correct that the higher fiber does provide protection of the intestinal mucosa. And this would not only protect against bacteria infection of the mucosa, but it should also be part of increasing the risk for colon cancers. The influence of bacteria on our cravings has had some evidence and now an excellent study on it. It is not surprising as we known that a variety of helminths and protozoal parasites affect animal and human behavior and so why not bacteria. We will probably find many ways in which they affect us as we study more, including how other species cause effects and the more difficult question of how combinations of microbes affect us. It reminds me of a conjecture paper that I have thought about writing and should probably get back to.

Robert John Wolff Yes! Please write this paper and send it to me when you're done. I'd appreciate reading more on this topic and seeing more articles and papers published on this topic.