Ammonia oxidizing microorganism preparations for delivery to the gastrointestinal system, kits including ammonia oxidizing preparations for delivery to the gastrointestinal system, and devices for administering ammonia oxidizing preparations to the gastrointestinal system are provided. Methods of introducing ammonia oxidizing microorganisms to the gastrointestinal system are provided. Methods of treating disorders, including gastrointestinal disorders and inflammatory disorders, with ammonia oxidizing microorganism preparations are provided.L'invention porte sur des micro-organismes, kits et dispositifs oxydant l'ammoniac dans le système gastro-intestinal, sur une méthode d'introduction de ces micro-organismes dans le système gastro-intestinal, et sur des procédés de traitement de troubles gastro-intestinaux et inflammatoires.