Clostridium difficile infection is the leading cause of hospital-associated gastrointestinal illness. It is typically treated with a course of antibiotics, but the infection recurs in about 20% of cases. C. difficile infections are difficult to eradicate because the bacteria exist in two forms: a replicating, toxin-producing form and a spore form that is resistant to antibiotics. Fecal microbiota transplantation—the transfer of normal gut microbiota from a healthy individual— can resolve >90% of recurrent infections, a much better cure rate than further antibiotic treatment alone. Why do you suppose microbiota transplantation is so effective?