Cell envelope disruption of E. coli Exposed to ϵ‐polylysine by FESEM and TEM technology

Abstract

To investigate the action mechanism of ϵ-polylysine (ϵ-PL) against Escherichia coli (E. coli), a new field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) technology has been developed. The log phase E. coli cells were first incubated with ϵ-PL for 8 min, then the samples were directly added onto the silicon platelet and the copper grid, followed by a simple in situ fixation and freezing dehydration. FESEM and TEM were used to examine the ultrastructure changes in the bacterial envelope which was affected by ϵ-PL. various damages of E. coli cell envelope by ϵ-PL have demonstrated the detachment of outer membrane, the swelling of inner membrane, the apical burst of cells and the leakage of cytosol at a minimal inhibitory concentration (MIC) concentration. It also exhibited whole cell lysis at double MIC concentration. In summary, the new FESEM and TEM technology and appropriate sample preparation protocols have been found to be useful for investigating the biocidal activity of ϵ-PL against E. coli.

Antibacterial activity of chemically versus enzymatic functionalized wool with ɛ-poly-L-lysine

“…In Figure 8 the presented representative fluorescence images after exposure to the bacterial strain show green labeled cells on the surface of all the tested samples, being much more intensive on the Ref-WO when compared to the other modified wool samples, where the presence of red bacteria indicates that "PL may destroy the cytoplasmic membranes of bacterial cells before lysis. Similar observations were reported recently by Zhou et al, 57 where various damage to the E. coli cell envelope by "PL demonstrated detachment of the outer membrane, swelling of the inner membrane, apical bursting of cells, and leakage of cytosol at a minimal inhibitory concentration. This hypothesis may also be supported by the already approved bactericidal effect of "PL by the Federal Drug Administration, 58 indicating that the bactericidal action of "PL against both bacteria is mediated by physical ionic interactions with the microbial cell wall inducing pore formation and/or disintegrating the cell membrane.…”

Synthesis of Berberine and Canagliflozin Chimera and Investigation into New Antibacterial Activity and Mechanisms

“…Dihydroberberine: a pale-yellow solid (75.0% yield); 1 H nmR (see Figure S1, 400 MHz, CDCl 3 ) δ 7.17 (s, 1H), 6.73 (s, 2H), 6.57 (s, 1H), 5.93 (t, J = 6.8 Hz, 3H), 4.32 (s, 2H), 3.84 (s, 6H), 3.13 (t, J = 5.6 Hz, 2H), 2.87 (t, J = 5.4 Hz, 2H) [27,28].…”

“…FESEM was performed as described by Zhou [27], with some modifications. Bacterial cells (~2 × 10 8 CFU/mL) were treated with CAN, BBR, B+C, BC at concentrations of 1/2MIC80 and incubated at 37 • C for 24 h. The cells were then harvested by centrifugation (4000× g 5 min, 4 • C) and rinsed twice with PBS.…”

pH-Triggered Controllable Release of Silver–Indole-3 Acetic Acid Complexes from Mesoporous Silica Nanoparticles (IBN-4) for Effectively Killing Malignant Bacteria

“…FE-SEM slides were prepared by following the procedure described by Zhou and colleagues . To visualize the whole cell morphology of E. coli after treatment with IBN-4-IAAH–Ag NPs, the cells of E. coli in the mid log phase were collected by centrifugation, rinsed three times in physiological saline (pH 7.0), and diluted to 1 × 10 5 CFU/mL final concentration with the same buffer.…”

“…FE-SEM slides were prepared by following the procedure described by Zhou and colleagues. 106 To visualize the whole cell morphology of E. coli after treatment with IBN-4-IAAH−Ag NPs, the cells of E. coli in the mid log phase were collected by centrifugation, rinsed three times in physiological saline (pH 7.0), and diluted to 1 × 10 5 CFU/mL final concentration with the same buffer. Interactions between bacterial strain (E. coli and S. aureus) and IBN-4-IAAH−Ag NPs at MIC concentration (30 μg/mL) were incubated in 37 °C for 8 min with 50 rpm orbital shaking to prevent clumping of the cells.…”