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.

Pediocin PA-1（PA-1）是一种来自乳酸菌的靶向膜细菌素，对多种革兰氏阳性病原体表现出抗菌活性。但是，革兰氏阴性细菌的外膜不允许pediocin进入其靶标。在这项工作中，分析了PA-1与L-乳酸对革兰氏阴性水产养殖和食物病原体嗜水气单胞菌（A. hydrophila）的协同抑制机理。3.5 mmol / L L-乳酸和50μmol/ L（或30μmol/ L）PA-1的组合处理具有很强的对亲水曲霉的抑菌和杀菌活性。全波长扫描和ELISA分析显示亲水性曲霉外膜释放脂多糖（LPS）L-乳酸引起的治疗。用FITC标记的pediocin PA-1对亲水性链球菌进行激光共聚焦显微镜成像，证明了PA-1在乳酸处理过的细菌细胞上的积累。然后，PA-1在乳酸处理过的嗜水链球菌中引起膜电位（Δψ）和质子梯度差（ΔpH）的快速耗散。Pediocin PA-1也引起细胞外ATP水平升高。SEM和TEM显示的形态学表明，乳酸和PA-1诱导的囊泡联合处理在细胞表面，内外膜破裂，甚至细胞质渗漏和细胞裂解。结果证明了乳酸和PA-1协同抑制嗜水链球菌的潜在机制。，L-乳酸释放外膜LPS，使PA-1可以接触亲水链球菌的质膜，从而导致内膜中质子动力的耗散和细胞死亡。