Ans. Microbial cells.
In humans, various symbiotic microorganism live in digestive tracts and are known as gut flora or gut microbiota, such as various bacteria and fungi.
These microorganisms provide immunity against some pathogenic microbes and help in digestion of some indigestible food compounds.
Examples of these microbial cells include Lactobacillus and E. coli.
Thus, the cells described here are 'cells of microorganisms' or 'microbial cells.'