Sinai A P, Bavoil P M
University of Rochester Medical Center, Department of Microbiology and Immunology, New York 14642.
Mol Microbiol. 1993 Dec;10(5):1125-37. doi: 10.1111/j.1365-2958.1993.tb00982.x.
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.
我们分离出了pst-phoU操纵子的两个转座子插入突变，这些突变导致phoA基因产物碱性磷酸酶的组成型表达。这两个突变还使大肠杆菌对培养的HEp-2细胞具有侵袭性，并定义了一种新的Pho调节的侵袭途径。在这些突变体中存在源自肠侵袭性大肠杆菌（EIEC）临床分离株的大型“侵袭”质粒，会导致对培养的HEp-2细胞的侵袭性增强，这种现象被称为“超侵袭性”表型。将pst-phoU插入突变转导到EIEC和福氏志贺氏菌的临床分离株中，会导致前者组成型表达PhoA并伴有超侵袭性，而后者则不会。我们推测，这里描述的Pho调节的侵袭途径，虽然在标准实验室丰富培养基中生长的细菌中是沉默的，但当侵袭性细菌遇到营养饥饿和/或其他相关应激条件时，可能在宿主体内发挥作用。
