CFBP1430 was mutagenized by phage MudllPR13 insertion Thirty prototrophic pathogenicity mutants with a single insertion were isolated. Among these, 17 non-pathogenic (Path) mutants were obtained; 11 of them were unable to induce a hypersensitive response (HR) on tobacco (Hrp mutants), whereas the remaining six were still able to do so (Dsp mutants). Thirteen other mutants showed reduced virulence (Rvi) and were still able to induce an HR. One of them appeared to be Path on apple seedlings and Rvi pear seedlings. All the Hrp mutants and all but three of the Dsp mutants mapped in the gene cluster previously reported. Some Rvi mutants also proved to map in this region; most of them, as well as two Dsp mutants map in an unknown genomic region. Cell-surface components thought to play a role in bacterial pathogenicity were examined, including exopolysaccharides (EPS), lipopolysaccharides (LPS), and outer-membrane proteins. One mutant only was found to be non-capsulated and unable to produce EPS. The insertion in this mutant mapped in a genomic cluster involved in amylovoran synthesis. Unlike the parental strain, some mutants exhibited sensitivity to the phage and this phenotype was associated with a modified LPS electrophoretic profile. Rvi mutants and some Path mutants were able to multiply to some extent; other Path mutants reached only a low population level, except the non-capsulated one, which rapidly decreased to an undetectable level.


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