Technical Abstract: The mechanisms governing the ability of bacteria to adhere to and colonize human and animal hosts in health and disease are still incompletely understood. Throughout the extensive mucosal surfaces of the body that are in contact with the external environment, epithelial cells represent the first point of cellular contact between bacteria and the host. Prokaryotic factors such as flagellin or intimin play important roles in epithelial adherence or invasion by commensal or pathogenic bacteria; physicochemical factors such as ambient temperature and pH contribute to bacterial colonization as well. The roles served by other, host-related factors in microbe-host interactions, such as host regulatory molecules, have recently been discovered. In this chapter, we will discuss the nature of intercellular communication that occurs among four key cells, i.e. intestinal epithelial cells, enteroendocrine cells, neurons and gut immunocytes, that participate in modulating interactions of bacteria with the intestinal mucosa. We will pay special consideration to the emerging role of host-derived biogenic amines in this process. One class of biogenic amines, the catecholamines, epinephrine, norepinephrine and dopamine, have been extensively studied over the past two decades for their direct effects on the growth and virulence properties of enteric bacteria.