The composition of our gut microbial community has been linked directly to our health, but researchers are only beginning to study the impact of its functional metabolic behavior, which can shift in response to external factors. Microbial production of H₂S in the gut is one such function, and it may be a colorectal cancer trigger. A recent study used publicly available datasets to examine the sulfur metabolism genes in our gut microbiota. Sulfur metabolism genes were more abundant and diverse than previously thought and were correlated with colorectal cancer. The researchers also examined two key sulfate reductases: dissimilatory sulfite reductases (Dsr) and anaerobic sulfite reductase (asr) and found that genes for asr were twice as abundant as genes for Dsr, suggesting that asr is a more important contributor to sulfate reduction in the human gut and found that genes for asr were twice as abundant as genes for Dsr, suggesting that asr is a more important contributor to sulfate reduction in the human gut. Both inorganic (i.e., sulfate) and organic (i.e., sulfur-containing amino acids) sulfur metabolism genes were associated with colorectal cancer. While in vivo studies are needed, this study expanded the current information about microbial sulfur metabolism in the human gut microbiome and provided further evidence that sulfidogenesis is correlated with colorectal cancer.