School of Life Sciences, Arizona State University, Tempe, AZ, USA.
Ann Clin Microbiol Antimicrob. 2010 Sep 16;9:26. doi: 10.1186/1476-0711-9-26.
We have previously identified two mineral mixtures, CB07 and BY07, and their respective aqueous leachates that exhibit in vitro antibacterial activity against a broad spectrum of pathogens. The present study assesses cellular ultrastructure and membrane integrity of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli after exposure to CB07 and BY07 aqueous leachates.
We used scanning and transmission electron microscopy to evaluate E. coli and MRSA ultrastructure and morphology following exposure to antibacterial leachates. Additionally, we employed Baclight LIVE/DEAD staining and flow cytometry to investigate the cellular membrane as a possible target for antibacterial activity.
Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging of E. coli and MRSA revealed intact cells following exposure to antibacterial mineral leachates. TEM images of MRSA showed disruption of the cytoplasmic contents, distorted cell shape, irregular membranes, and distorted septa of dividing cells. TEM images of E. coli exposed to leachates exhibited different patterns of cytoplasmic condensation with respect to the controls and no apparent change in cell envelope structure. Although bactericidal activity of the leachates occurs more rapidly in E. coli than in MRSA, LIVE/DEAD staining demonstrated that the membrane of E. coli remains intact, while the MRSA membrane is permeabilized following exposure to the leachates.
These data suggest that the leachate antibacterial mechanism of action differs for Gram-positive and Gram-negative organisms. Upon antibacterial mineral leachate exposure, structural integrity is retained, however, compromised membrane integrity accounts for bactericidal activity in Gram-positive, but not in Gram-negative cells.
我们之前已经鉴定出两种矿物混合物 CB07 和 BY07 及其各自的水提物，它们在体外对广谱病原体表现出抗菌活性。本研究评估了耐甲氧西林金黄色葡萄球菌 (MRSA) 和大肠杆菌在接触 CB07 和 BY07 水提物后细胞的超微结构和膜完整性。
我们使用扫描和透射电子显微镜来评估暴露于抗菌浸提液后大肠杆菌和 MRSA 的超微结构和形态。此外，我们还采用 Baclight LIVE/DEAD 染色和流式细胞术来研究细胞膜是否可能是抗菌活性的靶标。
扫描电子显微镜 (SEM) 和透射电子显微镜 (TEM) 成像显示，暴露于抗菌矿物浸提液后的大肠杆菌和 MRSA 细胞完整。MRSA 的 TEM 图像显示细胞质内容物破裂、细胞形状变形、细胞膜不规则和分裂细胞的隔膜变形。暴露于浸提液的大肠杆菌的 TEM 图像显示细胞质浓缩的模式与对照不同，细胞包膜结构没有明显变化。尽管浸提液对大肠杆菌的杀菌活性比 MRSA 更快，但 LIVE/DEAD 染色表明，暴露于浸提液后，大肠杆菌的膜保持完整，而 MRSA 的膜被渗透。
这些数据表明，浸提液对革兰氏阳性和革兰氏阴性生物的抗菌作用机制不同。在接触抗菌矿物浸提液后，结构完整性得以保留，然而，革兰氏阳性细胞的杀菌活性归因于受损的膜完整性，而不是革兰氏阴性细胞。
