没食子酸对水稻细菌性条斑病菌细胞结构的影响(英文)

Effects of gallic acid on cell structure of Xanthomonas oryzae pv. oryzicola

关键词:  水稻细菌性条斑病菌, 没食子酸, 细胞结构, 膜通透性,抑菌机制

Key words:  Xanthomonas oryzae pv. oryzicola, gallic acid, cell structure, membrane permeability, bacteriostasis me-chanism

摘要:

没食子酸(gallic acid, GA)是一种植物酚类化合物,具有多种生物活性。前期实验发现,GA对水稻细菌性条斑病菌(Xanthomonas oryzae pv. oryzicola, Xoc)具有较强的抑制作用。为了解该物质对Xoc的细胞结构和细胞膜的影响,该研究用电子显微镜观察GA对Xoc的形态结构的影响,通过测定GA处理后的Xoc培养液的电导率、紫外吸收物含量(260 nm的吸光值)、乳酸脱氢酶的活性以及菌体的二乙酸荧光素(fluorescein diacetate, FDA)的强度等,探讨了GA对Xoc细胞膜的完整性和通透性的影响。结果表明:经浓度为200 μg·mL^-1的 GA处理后,Xoc的菌体形态结构发生改变,表面有明显的凹陷或不规则囊泡状突起,表明GA对Xoc细胞壁有损伤作用。200 μg·mL^-1的GA处理24 h后,病菌培养液的电导率为135.48 μS·cm^-1(对照处理为127.85 μS·cm^-1)。GA处理2 h后,Xoc细胞荧光强度下降58.10%,说明病菌细胞内电解质外渗和细胞溶质发生渗漏; 同时,乳酸脱氢酶的活性增加,表明菌体的细胞膜受到破坏。此外,GA处理24 h后,Xoc培养液在260 nm下的吸光值为1.004(对照处理为0.018),表明病菌细胞膜的完整性受到破坏。这表明GA不仅破坏Xoc的细胞膜通透性,而且还影响膜的完整性。

Abstract:

Gallic acid(GA)is a phenolic compound, and presents various biological activities in plants. Our previous experiments demonstrated a relatively strong inhibitory effect of GA on Xanthomonas oryzae pv. oryzicola(Xoc). In order to elucidate the effects of GA on the cell structure and membrane permeability of the pathogen, morphological structures of bacteria treated with GA were observed by electron microscopy, the integrity and the permeabilities of membrane of Xoc were investigated by determining the release from cells of materials that absorb at 260 nm, and changes in the fluorescence of cells treated with the fluorescein diacetate(FDA)and lactate dehydrogenase(LDH)activity. After treating with 200 μg·mL^-1of GA, many pits and irregular vesicles were found on the cell surface under electron microscopy, indicating that GA could damage the cell walls of Xoc. The electrical conductivity from Xoc suspensions 24 h after GA treatment was 135.48 μS·cm^-1(that of control was 127.85 μS·cm^-1), and the fluorescence intensity of Xoc suspensions 2 h after GA decreased by 58.10%, indicating that cells leaked electrolytes and cytosolic contents. Meanwhile, the acti-vities of LDH in bacterial suspensions treated with GA also increased, suggesting that GA could damage the structure of the bacterial cell membrane. In addition, the absorbance at 260 nm from Xoc suspensions was 1.004(that of control was 0.018), indicating that GA could negatively affect Xoc cell wall integrity. These results indicate that GA can not only alter the permeability of the cell membrane of Xoc, but also can impact the integrity of cell membrane.