Al-Mijalli Samiah H S
Biology Department, College of Sciences, Nora Bent AbdulRahman University, Riyadh, Saudi Arabia.
3 Biotech. 2014 Aug;4(4):337-344. doi: 10.1007/s13205-013-0136-2. Epub 2013 Aug 14.
Forty-three bacterial isolates in five genera were recovered from naturally infected green pepper fruits (38 samples) showing dark brown, irregular-shaped splotches. The pathogenicity test was performed on healthy green pepper fruits and red colonies were from inoculated fruits showing the same symptoms and the infected area developed into soft rot. Their identification was based on phenotypic characters and sequence of the gene fragment coding 16S rRNA. Of 43 isolates, 10 showing splotches on green pepper fruits belonged to genus Serratia on the basis of phenotypic characters. One representative isolate of the genus Serratia has been identified by partial 16S rRNA gene sequencing and phylogenetic analysis as belonging to the Serratia rubidaea and has the potential to cause spot on green pepper. Eleven phytopathogenic bacterial isolates were also obtained at the same time but did not induce any splotch symptoms on artificially infected green pepper. Five out of 11 bacterial isolates were identified as Ralstonia on the basis of biochemical tests. Partial sequencing of 16S ribosomal gene of representative isolate revealed that the isolate is Ralstonia solanacearum. The six remaining isolates were related to Xanthomonas vesicatoria on the basis of biochemical tests. Twenty-two of opportunistic human pathogens were isolated at the same time and related to Proteus and Klebsiella. Opportunistic human pathogens did not produce any symptoms on artificially infected green pepper. One representative isolate for each genus was identified as Klebsiella oxytoca and Proteus mirabilis based on their partial 16S rRNA gene sequences. The virulence of the S. rubidaea, the causal agent of green pepper fruits splotches was attributed to the production and secretion of a large variety of enzymes capable of degrading the complex polysaccharides of the plant cell wall and membrane constituents.
从自然感染的青椒果实（38个样本）中分离出了五个属的43株细菌，这些果实呈现出深褐色、形状不规则的斑点。对健康青椒果实进行了致病性测试，接种果实上出现红色菌落，表现出相同症状，感染区域发展为软腐。它们的鉴定基于表型特征和编码16S rRNA的基因片段序列。在43株分离物中，根据表型特征，有10株在青椒果实上出现斑点的属于沙雷氏菌属。通过部分16S rRNA基因测序和系统发育分析鉴定出一株沙雷氏菌属的代表性分离物属于深红沙雷氏菌，它有可能导致青椒出现斑点。同时还获得了11株植物病原细菌分离物，但在人工感染的青椒上未诱导出任何斑点症状。根据生化测试，11株细菌分离物中有5株被鉴定为罗尔斯通氏菌属。代表性分离物的16S核糖体基因部分测序显示该分离物为青枯雷尔氏菌。根据生化测试，其余6株分离物与疮痂黄单胞菌有关。同时分离出22株机会性人类病原体，它们与变形杆菌属和克雷伯氏菌属有关。机会性人类病原体在人工感染的青椒上未产生任何症状。根据它们的部分16S rRNA基因序列，每个属的一株代表性分离物被鉴定为产酸克雷伯氏菌和奇异变形杆菌。青椒果实斑点病的病原菌深红沙雷氏菌的毒力归因于其产生和分泌的多种能够降解植物细胞壁复杂多糖和膜成分的酶。
