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Category: Microbial Genetics and Molecular Biology; Bacterial Pathogenesis
Escherichia coli Type 1 Pili, Page 1 of 2
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This chapter concentrates on what the author thinks are the essential features of Escherichia coli type 1 pili as models of host-pathogen interactions, gene regulation, supramolecular assembly, and receptor binding. The majority of E. coli strains fell into group 1, which had the structures that were to become known as type 1 pili. Type 1 pili grow from the base. That is, new pilin monomers (fimA gene products) are added to the bottom of the growing fiber rather than at the tip. There are only two additional gene products required for this polymerization process. These are the products of the fimC and fimD genes. A chaperone molecule is believed to be necessary in order to keep the pilin molecules from aggregating prematurely and to stabilize the minor pilus components during their time in the periplasm. Type 1 pili have provided paradigms for a number of central biological processes including host-pathogen interactions, gene regulation, assembly of supramolecular structures, and receptor-ligand interactions. The chapter highlights areas that still present interesting challenges to understanding of type 1 pili structures and their function.
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Electron micrograph of an E. coli cell with type 1 pili that has been negatively stained with 1.0% phosphotungstic acid. Bar, 0.25 µm.
Electron micrograph of an E. coli cell with type 1 pili that has been negatively stained with 1.0% phosphotungstic acid. Bar, 0.25 µm.
The fim genes are located at approximately 98 min on the E. coli genetic map ( 7 ). All of the genes are transcribed from left to right as drawn (clockwise on the map [35] ). The genetic mnemonics used throughout the text are from Bachmann ( 7 ) and are for E. coli K-12. In the initial descriptions of the genes ( 105 – 108 ), the pil and hyp designations were used (shown in parentheses in the illustration). The intercistronic regions are not drawn to scale in all cases. An additional open reading frame designated fimI has been reported ( 70 ); it is immediately to the right of fimA. Details of the function of the flmI gene product have not yet been communicated. More detailed explanations of gene function and additional references may be found in the text.
The fim genes are located at approximately 98 min on the E. coli genetic map ( 7 ). All of the genes are transcribed from left to right as drawn (clockwise on the map [35] ). The genetic mnemonics used throughout the text are from Bachmann ( 7 ) and are for E. coli K-12. In the initial descriptions of the genes ( 105 – 108 ), the pil and hyp designations were used (shown in parentheses in the illustration). The intercistronic regions are not drawn to scale in all cases. An additional open reading frame designated fimI has been reported ( 70 ); it is immediately to the right of fimA. Details of the function of the flmI gene product have not yet been communicated. More detailed explanations of gene function and additional references may be found in the text.
The fim genes are located at approximately 98 min on the E. coli genetic map ( 7 ). All of the genes are transcribed from left to right as drawn (clockwise on the map [35] ). The genetic mnemonics used throughout the text are from Bachmann ( 7 ) and are for E. coli K-12. In the initial descriptions of the genes ( 105 – 108 ), the pil and hyp designations were used (shown in parentheses in the illustration). The intercistronic regions are not drawn to scale in all cases. An additional open reading frame designated fimI has been reported ( 70 ); it is immediately to the right of fimA. Details of the function of the flmI gene product have not yet been communicated. More detailed explanations of gene function and additional references may be found in the text.
The fim genes are located at approximately 98 min on the E. coli genetic map ( 7 ). All of the genes are transcribed from left to right as drawn (clockwise on the map [35] ). The genetic mnemonics used throughout the text are from Bachmann ( 7 ) and are for E. coli K-12. In the initial descriptions of the genes ( 105 – 108 ), the pil and hyp designations were used (shown in parentheses in the illustration). The intercistronic regions are not drawn to scale in all cases. An additional open reading frame designated fimI has been reported ( 70 ); it is immediately to the right of fimA. Details of the function of the flmI gene product have not yet been communicated. More detailed explanations of gene function and additional references may be found in the text.
Electron micrographs of negatively stained E. coli cells that have lesions in genes producing two of the minor pilus components (after Russell and Orndorff [116] ). (A) The parental stain showing pili of normal numbers per cell and length. (B) A fimF mutant that produces approximately one-fourth the number of pili produced by the parent. (C) A fimG mutant that produces pili that are two to three times longer than those of the parent. (D) A fimF-fimG double mutant that produces fewer and longer pili than the parent. Bar, 0.25 µm.
Electron micrographs of negatively stained E. coli cells that have lesions in genes producing two of the minor pilus components (after Russell and Orndorff [116] ). (A) The parental stain showing pili of normal numbers per cell and length. (B) A fimF mutant that produces approximately one-fourth the number of pili produced by the parent. (C) A fimG mutant that produces pili that are two to three times longer than those of the parent. (D) A fimF-fimG double mutant that produces fewer and longer pili than the parent. Bar, 0.25 µm.