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Microcin E492 antibacterial activity: evidence for a TonB-dependent inner membrane permeabilization on Escherichia coli (2003)

Destoumieux-Garzón, Delphine ; Thomas, Xavier ; Santamaria, Mónica ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 49 (2003), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: The mechanism of action of microcin E492 (MccE492) was investigated for the first time in live bacteria. MccE492 was expressed and purified to homogeneity through an optimized large-scale procedure. Highly purified MccE492 showed potent antibacterial activity at minimal inhibitory concentrations in the range of 0.02–1.2 µM. The microcin bactericidal spectrum of activity was found to be restricted to Enterobacteriaceae and specifically directed against Escherichia and Salmonella species. Isogenic bacteria that possessed mutations in membrane proteins, particularly of the TonB–ExbB–ExbD complex, were assayed. The microcin bactericidal activity was shown to be TonB- and energy-dependent, supporting the hypothesis that the mechanism of action is receptor mediated. In addition, MccE492 depolarized and permeabilized the E. coli cytoplasmic membrane. The membrane depolarization was TonB dependent. From this study, we propose that MccE492 is recognized by iron-siderophore receptors, including FepA, which promote its import across the outer membrane via a TonB- and energy-dependent pathway. MccE492 then inserts into the inner membrane, whereupon the potential becomes destabilized by pore formation. Because cytoplasmic membrane permeabilization of MccE492 occurs beneath the threshold of the bactericidal concentration and does not result in cell lysis, the cytoplasmic membrane is not hypothesized to be the sole target of MccE492.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03610.x

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Electronic core level microanalyses and microscopies in multipurpose apparatus (1989)

Cazaux, Jacques ; Gramari, Daniel ; Jbara, Omar ; [et al.]

New York, NY : Wiley-Blackwell

Journal of Electron Microscopy Technique 11 (1989), S. 222-229

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ISSN: 0741-0581

Keywords: Electron spectroscopies ; Electron probe microanalysis ; X-ray spectroscopy ; Scanning X-ray radiography ; Surface analysis ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Natural Sciences in General

Notes: Using an instrument equipped with two electron guns, an electron analyzer, and a Si(Li) diode detector, we developed microanalytical techniques based on inner-shell electron excitations by incident electrons and X-rays, that is, electron energy-loss spectroscopy (EELS) in the reflection mode; electron probe microanalysis (EPMA) and X-ray appearance potential spectroscopy (XAPS); electron-induced Auger electron spectroscopy (e-AES); X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS); X-ray induced AES (XAES), X-ray fluorescence analysis (XRF), and scanning X-ray radiography (SXR). The corresponding characteristic images (including X-ray microradiography and X-ray photoelectron microscopy) were obtained in the scanning mode. The principle of the apparatus is described. Each spectroscopy and microscopy is illustrated by an example. Their performance and limits are discussed.

Additional Material: 14 Ill.