A gastrointestinal device and methods of manufacturing said gastrointestinal device are described and include a flexible tubular structure including an inner surface and an outer surface, at least one microbe-promoting agent associated with at least one of the inner surface and the outer surface, the at least one microbe-promoting agent configured to promote attraction, colonization, and growth of at least one type of commensal microbe, and a proximal end and a distal end, the proximal end and the distal end forming a flow conduit through the flexible tubular structure; and at least one anchor structure including one or more gastric wall-engaging components configured to engage a wall of the gastrointestinal tract of the subject.