Final answer:
The predominant anaerobic bacteria in the human colon is Bacteroides fragilis, accounting for about 30% of the gut microbiome and playing a mutualistic role in maintaining gut health.
Step-by-step explanation:
The predominant anaerobic bacteria found in the human colon is Bacteroides fragilis. This genus, specifically the Bacteroides, represents a significant portion of the microbes in the human gut, accounting for about 30% of the total gut microbiome. One gram of human feces can contain up to 100 billion Bacteroides cells.
These bacteria are usually mutualistic, providing benefits such as preventing pathogens from colonizing the large intestine. However, when their populations are diminished, such as after antibiotic use, the gut can become more susceptible to colonization by pathogenic bacteria and fungi.