不同pH下胞外多糖和脂多糖对烟草青枯菌根部定殖的影响

摘要

In this study, the difference of the secretion of exopolysaccharides and lipopolysaccharide of R.solanacearum and their effects on the number of R. solanacearum adsorbed in tobacco roots were studied at different pH values. The results showed that the maximum single and total yield of EPS were 3.27×10-12 and 50.12×10-2 g at pH 6.5, respectively. While the minimum single and total yield of EPS were at pH 8.0. The maximum total yield of LPS was 9.41×10-3 g at pH 7.0, and the maximum single yield was 17.51×10-15 g at pH 7.5; In addition, the single yield of EPS was much higher than LPS at the same pH value. EPS had a promotive effect on the adsorption and invasion of R.solanacearum in tobacco roots, while LPS had a suppressive effect, and the promotive effect of EPS played a major role at the same concentration. When added EPS under the pH6.6, the number of R.solanacearum adsorbed and invaded in the root surface were the maximum, reaching 15.43×108 and 10.73×109 cfu/g mf (fresh matter) respectively, and the bacterial number of R.solanacearum deposited on the root surface and clogged in the cross section with its secretion were the most, and root tip deformitied seriously. Therefore, EPS secretion was increased under acidic conditions, which promoted the identification and adsorption of R.solanacearum on tobacco roots, and the degree of disease occurrence was further improved. LPS secretion was increased under neutral and alkaline conditions, which reduced disease occurrence.%通过设定不同pH梯度,研究烟草青枯菌胞外多糖(Exopolysaccharides,EPS)和脂多糖(Lipopolysaccride,LPS)分泌量的差异及其对烟草根部吸附青枯菌数量的影响.结果表明,pH为6.5时EPS单产量和总产量均最大,分别达到3.27×10-12和50.12×10-2 g,pH 8.0时总产量和单产量最小.pH 7.0时,LPS的总产量最大,为9.41×10-3 g,pH 7.5时单产量最大,为17.51×10-15 g.同一pH梯度的EPS单产量远大于LPS单产量.EPS促进烟株根部吸附和侵入青枯菌,而LPS起抑制作用,且相同浓度下EPS促进作用占主导.当pH为6.6时,添加EPS的菌液处理的烟株根表吸附和根内侵入青枯菌数量最大,分别达到15.43×108和10.73×109 cfu/g;堆积在根表的杆状青枯菌菌体及导管横切面堵塞的青枯菌及其分泌物的数量最多,根尖畸形严重.因此,偏酸性条件下,青枯病菌EPS分泌量增多,促进青枯菌与烟草根部的识别和吸附,进一步提高病害发生程度,而中性和偏碱性条件有利于LPS分泌,降低病害发生.