Studying the host-microbiota interaction in the human gastrointestinal tract: basic concepts and in vitro approaches

Bacteria in the human gut exceed the number of cells in our body by a 100-fold. At the level of the gastrointestinal epithelium, a constant battle is fought for equilibrium between the microbiota and the human body. These interactions play a key role in many aspects of host health, influencing energy harvest from food, colonization by pathogens, and the immune system, to name but a few. Unfortunately, the study of this host–microbiota interaction in vivo is limited by the inaccessibility of the digestive tract. Therefore, in vitro technology that focuses on the simulation of this epithelial environment offers an ideal platform with which to conduct mechanistic research that could shed more light on this environment and help explain in vivo observations. However, the limitation of currently available tools could yield results with limited reliability for an in vivo situation. The aim of this mini-review is to focus on the importance of studying the host–microbiota interaction in the gastrointestinal tract and to evaluate the state of the art of the available in vitro techniques. Finally, we aim to identify those missing factors that, if present, would allow the creation of a model that would constitute a better simulation of biofilm formation, i.e. one more closely resembling the in vivo situation.