FIG. 5.
Scanning electron micrographs of PhoPc S. typhimurium strain CS022 (A to D) and prgH mutant strain IB040 (E and F). Almost all of the S. typhimurium CS022 cells observed on Caco-2 cells lacked the short filamentous appendages observed on other strains (A), although two which exhibited such features were found (B). S. typhimurium CS022 cells observed on MDCK cells (data not shown) and on murine Peyer’s patch epithelia (C) invariably lacked these surface features, as did those adhering to cell-free culture supports (D), although longer filamentous appendages were occasionally observed. S. typhimurium IB040 cells frequently formed numerous short filamentous appendages when they adhered to Caco-2 cells (E), while such features were rarely observed on strain IB040 bacteria adhering to MDCK cells (F). Most of the cell-adhered bacteria of strain IB040 were present in dense aggregates linked by long filaments (F), which resembled the adherence pattern of invA mutant strain SB111 (compare Fig. 4F with Fig. 2A). Bars, 2 μm.