Pseudomonas aeruginosa is a Gram-negative opportunistic bacterial pathogen. Successful injection of virulence factors into host cells, evasion of phagocytosis and promotion of pathogenesis depend primarily on the function of type III secretion system (T3SS). A complex set of signaling pathways have been shown to modulate T3SS expression. In this review, a brief introduction is given on the composition, function, and molecular determinants...