Résumé
Expression of fimbriation was studied in Escherichia coli K-12 CA8000 HfrH, and its cya, crp and MS2 resistant mutants. The cells of cya+ crp+ parent strain were observed to be flagellated bacilli, lacking fimbriae, unable to agglutinate erythrocytes and deficient in ability to produce surface pellicle during growth in stationary culture. The cells of cya and crp mutants were observed to be cocci or coccobacilli devoid of flagella, having haemagglutinating activity, fimbriated and capable of producing surface pellicle in stationary cultures. The fimbriation and haemagglutinating activities were lower in cya mutants grown with cAMP supplementation. The cya and crp mutants produced relatively small, smooth and compact colonies consisting mostly of fimbriated cells, like those of earlier described Fim σ mutants. The cya+ crp+ MS2 resistant mutant produced large sized colonies like those of parent but was deficient in conjugal donor ability. It resembled cya and crp mutants in haemagglutinating and fimbriation properties. The cya and crp mutants have been earlier shown to be deficient in several Tra functions including conjugal donor ability. It is concluded that Escherichia coli K-12 cells express fimbriation when Tra functions of F-plasmid carried in them are not expressed either due to deficiency of active cAMPreceptor protein complex or mutation in F-plasmid or when F-plasmid is absent.