地毯草黄单胞菌分泌黄原胶的电镜观察

摘  要  为了研究地毯草黄单胞菌（Xanthomonas axonopodis）FJAT-10151产黄原胶的分泌行为，采用比浊法测定地毯草黄单胞菌的生长曲线，干重法测定黄原胶产量，2，4-二硝基苯肼显色法测定黄原胶中丙酮酸含量变化，通过扫描電子显微镜镜（SEM）和透射电子显微镜镜（TEM）观察地毯草黄单胞菌产黄原胶的分泌行为。FJAT-10151在发酵时间0～26 h为对数期，26～72 h为稳定期。菌株FJAT-10151为短杆状（约2 μm），端生鞭毛（约7.9 μm），菌体外面形成了一层较厚的荚膜，且许多菌体通过黄原胶连在一起，分泌的黄原胶呈棒状和网状2种形态，聚集或缠绕在细胞表面，其含量随发酵时间的延长而增加。菌株FJAT-10151发酵72 h可获得高品质黄原胶，其产量及丙酮酸含量最高。

关键词  地毯草黄单胞菌;黄原胶;显微观察;丙酮酸中图分类号  S31      文献标识码  A

Xanthan Gum Secreted by Xanthomonas axonopodis

ZHENG Meixia， ZHU Yujing^*， LIU Bo^*， CHEN Zheng， HUANG Sufang

Agricultural Bio-Resources Research Institute， Fujian Academy of Agricultural Sciences， Fuzhou， Fujian 350003， China

Abstract  In order to study the xanthan gum secreted by Xanthomonas axonopodis FJAT-10151， The growth curve of FJAT-10151 was determined by the turbidimetric method. The yield of xanthan gum was determined by the dry-weighing method. The content of pyruvic acid was determined by the 2，4-dinitrobenzene hydrazine chromogenic method. The secretion of xanthan gum from X. axonopodis was studied by SEM and TEM. The result showed that the logarithmic phase and stable phase of FJAT-10151 was 0–26 h and 26–72 h， respectively. FJAT-10151 was a short rod of 2 μm long with 7.9 μm of flagellum on the ends， and formed a thick capsule outside， and many bacteria together with xanthan gum. Xanthan gum had flake and filamentous forms， and gathered or wrapped around FJAT-10151 surface. The yield of xanthan gum increased with the extension of fermentation time. The yield of xanthan gum and pyruvic acid reached the highest at the fermentation time of 72 h. We could obtain high quality of xanthan gum at the fermentation time of 72 h.

Keywords  Xanthomonas axonopodis; xanthan gum; microscopic observation; pyruvic acid

DOI  10.3969/j.issn.1000-2561.2019.01.027

地毯草黄单胞菌（Xanthomonas axonopodis）为典型的植物致病菌。地毯草黄单胞菌会引起细菌性叶斑病^[1]，李淑彬等^[2]报道了红掌对该病菌高度敏感，离体叶片接种第4天、盆栽植株接种第8天后，病叶率达到100%，红掌叶片感染地毯草黄单胞菌初期出现水渍状病斑，之后病斑面积不断扩大，病斑颜色加深逐渐变成灰褐色，后期整个叶片呈灰褐色腐烂状态。地毯草黄单胞也会导致棉豆的白叶枯病^[3]和柑橘溃疡病^[4]等植物病害，该菌分泌胞外杂多糖黄原胶是致病原因之一^[5-6]。郑梅霞等^[7]筛选获得了一株分离自福建顺昌黄龙病红心柚叶片的高产黄原胶的地毯草黄单胞菌。