Fig. 6. Effect of overexpression of MxiH in Shigella on the length of type III secretion needles. (A) Electron micrograph of the purified type III secretion complexes from the mxiH mutant harboring pKT001 (cloned mxiH gene). Bacteria were grown in L-broth and induced with 1 mM IPTG. Scale bar, 100 nm. (B) Distribution of needle lengths in the type III secretion complexes purified from the mxiH mutant harboring pKT001 grown in L-broth with 1 mM IPTG. (C) Electron micrographs of the mxiH mutant harboring pKT001 grown in L-broth with 1 mM IPTG (a) or without IPTG (b). Arrowheads are indicative of the long needle structures in type III secretion complexes protruding from the cell surface. Scale bars, 100 nm.