What most common bacterial species that normally inhabits the human intestines?

The most common bacterial species that normally inhabit the human intestines include Bacteroides, Firmicutes (such as Lactobacillus and Clostridium), and Escherichia coli. These bacteria play essential roles in digestion, metabolism, and maintaining gut health. They contribute to the fermentation of dietary fibers and the production of short-chain fatty acids, which are beneficial for overall health. The diversity and balance of these microbial species are crucial for a well-functioning gastrointestinal system.