The role offim-linked genes and the eda gene in the ability of Escherichia coli to colonize the streptomycin-treated mouse intestine

Streptomycin-resistant E. coli K-12 and E. coli F-18 are excellent colonizers of the streptomycin-treated mouse intestine. E. coli F-18 fimA$\sp-$, constructed by bacteriophage P1 transduction of fimA$\sp-$ from E. coli K-12 fimA$\sp-$, was previously shown to occupy a secondary niche in the streptomycin-treated mouse intestine. This dissertation demonstrates that a fim-liked gene, gntP (encoding a gluconate permease), when transferred from E. coli K-12 to E. coli F-18, allows the E. coli F-18 recipient (when in competition with E. coli F-18) to occupy a secondary niche in the intestine. Since the uxu genes (encoding enzymes for glucuronate breakdown) are located directly downstream from the fim gene cluster, E. coli F-18 nut$\sp+$ uxuA$\sp-$ strains were tested for their capacity to occupy a secondary niche. E. coli F-18 $nut\sp+uxu$A$\sp-$ mutants were shown to occupy this secondary niche, and it was concluded that the uxuA and nut genes were not identical. Indeed E. coli F-18 complemented with plasmid pRU1 (containing gntP) occupies a secondary niche when in direct competition with E. coli F-18 in the mouse intestine. However E. coli uxuA$\sp-$ mutants showed a decreased colonizing ability in comparison to their parental strain, thus indicating the utilization of glucuronate during colonization. To further investigate the possible role of gluconate, $E.\ coli\ eda\sp-$ and $edd\sp-$ (Entner Doudoroff pathway genes) strains were constructed by insertional mutagenesis. Both E. coli K-12 $eda\sp-$ and E. coli F-18 $eda\sp-$ mutants were unable to colonize regardless of whether fed to mice alone, or when fed in competition with the corresponding wild type strain. Complete colonizing ability was restored when these $eda\sp-$ mutants were complemented with plasmid pTC190 (containing eda). Spontaneous $eda\sp-\ edd\sp-\ E.\ coli$ mutants, which do not accumulate KDPG in the presence of gluconate, were shown to be excellent colonizers. In vitro experiments confirm previous reports that the presence of gluconate inhibits the growth of $E.\ coli\ eda\sp-$ mutants. The data presented here demonstrate the role of the fim-linked gntP and uxuA genes, the requirement of a functional eda gene, and the utilization of gluconate and glucuronate (via the Ashwell and Entner Doudoroff pathways) for the colonization of the streptomycin-treated mouse intestine by E. coli K-12 and F-18