Lactobacillus reuteri is a gram-positive, commensal bacterium. It is the only lactobacillus bacteria found to be a major component of the human gut microbiota. It has been found to produce antibiotics that kill "bad" bacteria while sparing "good" bacteria. It reduces but does not fully eradicate helicobacter pylori infection. It is also important in the biosynthesis of Vitamin B12.
In rats, it was found to reduce bacterial translocation.