Clostridioides difficile is an opportunistic diarrheal pathogen responsible for significant morbidity and mortality worldwide. A disrupted (dysbiotic) gut microbiome, commonly engendered by antibiotic treatment, is the primary risk factor for C. difficile infection, highlighting that C. difficile–microbiome interactions are critical for determining the fitness of this pathogen. Here, we review short chain fatty acids (SCFAs): a major class of metabolites present in the gut, their production by the gut microbiome, and their impacts on the biology of the host and of C. difficile. We use these observations to illustrate a conceptual model whereby C. difficile senses and responds to SCFAs as a marker of a healthy gut and tunes its virulence accordingly in order to maintain dysbiosis. Future work to learn the molecular mechanisms and genetic circuitry underlying the relationships between C. difficile and SCFAs will help to identify precision approaches, distinct from antibiotics and fecal transplant, for mitigating disease caused by C. difficile and will inform similar investigations into other gastrointestinal pathogens.

Despite being widely regarded as generalist predators, amphibians exhibit a diversity of tooth shapes and dentition patterns, which may indicate the influence of dietary specialization on the evolution of tooth morphology. Very few studies have analysed the relationship between tooth morphology and diet (i.e., prey items) in amphibians, and those existing studies are highly speculative. We investigated the evolution of salamander teeth and the relationship between tooth morphology and diet in a phylogenetically independent fashion. We used a phylogeny of 23 species of salamander representing three families (Ambystomatidae, Plethodontidae, and Salamandridae) to, first, analyse the divergence of tooth morphology and its relationship to phylogeny and, second, to analyse the relationship between tooth morphology and diet diversity. We used electron scanning microscopy and a statistical comparative approach using Spatial Evolutionary and Ecological Analysis (SEEVA) and phylogenetic generalized least‐squares regression in R. Our results indicated significant divergence in tooth morphology at major phylogenetic splits. Moreover, there was a significant, phylogenetically independent relationship between tooth morphology and diet diversity. The relationship between diet and tooth morphology indicates not only a reflection of phylogenetic history, but also a degree of dietary specialization, indicating that evolution in tooth morphology has had an adaptive aspect in relation to salamander diet.