Tianjin Key Laboratory of Aqua-ecology and Aquaculture, College of Fisheries, Tianjin Agricultural University, 22 Jinjing Road, 300384 Tianjin, China.
Tianjin Key Laboratory of Aqua-ecology and Aquaculture, College of Fisheries, Tianjin Agricultural University, 22 Jinjing Road, 300384 Tianjin, China.
Biochim Biophys Acta Biomembr. 2020 Oct 1;1862(10):183346. doi: 10.1016/j.bbamem.2020.183346. Epub 2020 May 16.
Pediocin PA-1 (PA-1) is a membrane-targeting bacteriocin from lactic acid bacteria, which shows antimicrobial activity against a wide range of Gram-positive pathogens. However, the outer membrane of Gram-negative bacteria does not allow pediocin access to its target. In this work, the synergistic inhibitory mechanism of PA-1 with L-lactic acid against Gram-negative aquaculture and food pathogen Aeromonas hydrophila (A. hydrophila) was analyzed. The combined treatment of 3.5 mmol/L L-lactic acid and 50 μmol/L (or 30 μmol/L) PA-1 had strong bacteriostatic and bactericidal activity against A. hydrophila. Full wavelength scanning and ELISA assay revealed the release of lipopolysaccharide (LPS) from the outer membrane of A. hydrophila caused by L-lactic acid treatment. Laser confocal microscopic imaging of A. hydrophila with FITC-labeled pediocin PA-1 proved the accumulation of PA-1 on lactic acid-treated bacterial cells. PA-1 then caused a rapid dissipation of membrane potential (Δψ) and a proton gradient difference (ΔpH) in lactic acid-treated A. hydrophila. Pediocin PA-1 also caused an increase in the extracellular ATP level. Morphology revealed by SEM and TEM showed that combined treating with lactic acid and PA-1 induced vesicles on the cell surface, the outer and inner membrane disruption, and even cytoplasm leakage and cell lysis. The results proved a potential mechanism of the synergistic inhibition of lactic acid and PA-1 against A. hydrophila, by which L-lactic acid released the outer membrane LPS, making it possible for PA-1 to contact the plasma membrane of A. hydrophila, resulting in the dissipation of proton-motive force in the inner membrane and cell death.
肠菌素 PA-1（PA-1）是一种来自乳酸菌的膜靶向细菌素，对广泛的革兰氏阳性病原体具有抗菌活性。然而，革兰氏阴性细菌的外膜不允许肠菌素进入其靶标。在这项工作中，分析了 PA-1 与 L-乳酸协同抑制革兰氏阴性水产养殖和食品病原体嗜水气单胞菌（A. hydrophila）的机制。3.5mmol/L L-乳酸和 50μmol/L（或 30μmol/L）PA-1 的联合处理对 A. hydrophila 具有很强的抑菌和杀菌活性。全波长扫描和 ELISA 检测显示，L-乳酸处理导致 A. hydrophila 外膜中脂多糖（LPS）的释放。用 FITC 标记的肠菌素 PA-1 对 A. hydrophila 的激光共聚焦显微镜成像证明了 PA-1 在乳酸处理的细菌细胞上的积累。PA-1 随后导致乳酸处理的 A. hydrophila 中膜电位（Δψ）和质子梯度差（ΔpH）的快速耗散。肠菌素 PA-1 还导致细胞外 ATP 水平升高。SEM 和 TEM 观察到的形态学显示，乳酸和 PA-1 的联合处理在细胞表面诱导出小泡，破坏外膜和内膜，甚至导致细胞质泄漏和细胞裂解。结果证明了乳酸和 PA-1 协同抑制 A. hydrophila 的潜在机制，其中 L-乳酸释放外膜 LPS，使 PA-1 能够接触 A. hydrophila 的质膜，导致内膜质子动力丧失和细胞死亡。
