Component of the type III secretion system (T3SS), also called injectisome, which is used to inject bacterial effector proteins into eukaryotic host cells (PubMed:10406797). Forms a ring-shaped multimeric structure with an apparent central pore in the outer membrane (By similarity). Required for secretion of some type III-secreted effectors including the SpvB exotoxin (PubMed:10406797). The core secretion machinery of the T3SS is composed of approximately 20 different proteins, including cytoplasmic components, a base, an export apparatus and a needle. This subunit is part of the base, which anchors the injectisome in the bacterial cell envelope. Forms a stable homooligomeric complex. Does not survive in murine macrophages, although it can invade epithelial cells. The SpiC protein is not exported into host macrophage cells. Belongs to the bacterial secretin family. T3SS SctC subfamily.