Expression of SssF. (A) Western blot analysis of whole-cell lysates prepared from S. saprophyticus MS1146, MS1146sssF and MS1146sssF(pSssF) using a polyclonal antiserum directed against SssF. Lanes: M, Novex Sharp Pre-stained protein marker (Invitrogen); 1, MS1146; 2, MS1146sssF; 3, MS1146sssF(pSssF). The position of SssF is indicated. Expression of SssF was detected in wild-type S. saprophyticus strain MS1146 and the sssF complemented strain but not in the isogenic sssF mutant. (B) Immunogold TEM of S. saprophyticus MS1146, MS1146sssF and MS1146sssF(pSssF). Expression of SssF at the cell surface of S. saprophyticus MS1146 was demonstrated by abundant labeling with SssF-gold particles. In contrast, the sssF isogenic knockout mutant was devoid of gold labeling. Complementation of the sssF mutation restored and enhanced surface expression of SssF. Bars, 500 nm.