Hyper-invasive mutants define a novel Pho-regulated invasion pathway in Escherichia coli.
We have isolated two transposon insertion mutations of the pst-phoU operon which result in the constitutive expression of the phoA gene product, alkaline phosphatase. The two mutations also render Escherichia coli invasive towards cultured HEp-2 cells and define a novel Pho-regulated invasion pathway. The presence of the large 'invasion' plasmid derived from an entero-invasive E. coli (EIEC) clinical isolate in these mutants leads to enhanced invasiveness toward cultured HEp-2 cells, a phenomenon referred to as the 'hyper-invasive' phenotype. Transduction of a pst-phoU insertion mutation into clinical isolates of EIEC and Shigella flexneri results in constitutive PhoA expression and coupled hyper-invasiveness in the former but not the latter. We speculate that the Pho-regulated invasion pathway described here, while silent in bacteria grown in standard laboratory rich media, may become functional in the host when invasive bacteria encounter nutrient starvation and/or other related stress conditions.
Sinai
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AP
University of Rochester Medical Center, Department of Microbiology and Immunology, New York 14642.
Bavoil
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PM
D000469:Alkaline Phosphatase / Q000235:genetics; D000942:Antigens, Bacterial / Q000235:genetics; D001483:Base Sequence; D002460:Cell Line; D002874:Chromosome Mapping; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D012763:Shigella flexneri / Q000235:genetics / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics
D000942:Antigens, Bacterial; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D000469:Alkaline Phosphatase