polygalacturonic-acid and gluconic-acid

The oxygen sensor Aer of Escherichia coli affects the expression level of genes that are involved in sugar acid degradation. Phenotypes of Aer mediated gene regulation, namely growth on sugar acids was tested 'in vitro' with Phenotype MicroArrays and colonization of the mouse large intestine was tested 'in vivo'. The aer mutant did not grow on the sugar acids D: -gluconate, D: -glucuronate, D: -galacturonate, as well as the sugar alcohol D: -mannitol. Since sugar acids are the predominant carbon source for E. coli in the intestinal mucosa, the ability of the aer mutant to colonize the streptomycin-treated mouse large intestine was tested. The mutant exhibited a decreased ability to colonize the intestine when compared to wild-type cells. This effect was more pronounced under competitive conditions. The colonization phenotype of the aer mutant was complemented with either of two plasmids. One of them expressed the Aer protein, whereas the other one expressed the sugar acid degradation enzymes that are encoded by edd and eda. The data support the interpretation that decreased expression of edd and eda along with the decreased ability to grow on sugar acids may contribute to the reduced capacity of the aer mutant to colonize the mouse intestine. While Aer seems to be important during the initiation phase of colonization, FlhD/FlhC appears to be of disadvantage during maintenance phase. FlhD/FlhC is the master regulator of all flagellar genes and required for Aer expression. Mutants in flhD exhibited an initial competitive disadvantage during the first 3 days of colonization, but recovered lateron.

Topics: Animals; Carrier Proteins; Escherichia coli; Escherichia coli Proteins; Female; Gluconates; Glucuronates; Hexuronic Acids; Intercellular Signaling Peptides and Proteins; Intestine, Large; Mannitol; Mice; Plasmids; Trans-Activators; Virulence; Virulence Factors

The Escherichia coli human fecal isolates F-18 and K-12 are excellent colonizers of the streptomycin-treated mouse intestine. E. coli F-18 and E. coli K-12 eda mutants (unable to utilize glucuronate, galacturonate, and gluconate) were constructed by insertional mutagenesis. Neither the E. coli F-18 eda nor the E. coli K-12 eda mutant was able to colonize the streptomycin-treated mouse intestine, whether they were fed to mice together with their respective parental strains or alone. Complementation of the eda mutants with pTC190 (containing a functional E. coli K-12 eda gene) completely restored the colonization ability of both eda mutants. Relative to their parental strains, the E. coli F-18 eda mutant and the E. coli K-12 eda mutant grew poorly in cecal mucus isolated from mice fed either normal mouse chow or a synthetic diet containing sucrose as the sole carbon source, yet the mutants and parental strains demonstrated identical growth rates in minimal medium with glucose as the carbon source. E. coli F-18 edd eda and E. coli K-12 edd eda double mutants colonized the streptomycin-treated intestine when fed to mice alone; however, when fed simultaneously with their respective parental strains, they were poor colonizers. Since the edd gene is involved only in gluconate metabolism via the Entner-Doudoroff pathway, these results implicate the utilization of gluconate and the Entner-Doudoroff pathway as important elements in E. coli colonization of the streptomycin-treated mouse large intestine.

Topics: Animals; Cecum; Escherichia coli; Genetic Complementation Test; Gluconates; Glucuronates; Glucuronic Acid; Hexuronic Acids; Intestinal Mucosa; Mice; Mice, Inbred Strains

Topics: Gluconates; Hexuronic Acids; Keto Acids; Oxidation-Reduction