The present invention provides a method, wherein the method forms a biofilm, wherein the biofilm comprises a population of at least one bacterial strain attached to particles, wherein the biofilm is configured to colonize a gut of a subject in need thereof for at least five days, when ingested by the subject, the method comprising: a. obtaining a population comprising at least one strain of bacteria； b. inoculating a growth medium containing particles with the population comprising at least one strain of bacteria； c. incubating the particles with the population comprising at least one bacterial strain for a time sufficient for the population of at least one strain of bacteria to attach to the particles； and d. culturing the population comprising at least one strain of bacteria attached to the particles in a growth medium, for a time sufficient to form a biofilm.
