本研究在广东省及其周边地区共11个采样地点采集土壤样品156份，分离得到放线菌1026株。土壤预处理采用碳酸钙富集培养法，分离采用平板稀释法，选取高氏一号合成培养基作为分离培养基，添加50 mg/L重铬酸钾作为抑制剂。初筛采用琼脂块法，选择金黄色葡萄球菌、枯草芽孢杆菌、大肠埃希氏菌、白假丝酵母菌、黑曲霉共5种指示菌进行抑菌试验，共得到95株活性菌株。复筛选择初筛的5种指示菌加上副溶血性弧菌、铜绿假单胞菌、变形杆菌共8种指示菌，分两级进行复筛：一级复筛仍采用琼脂块，得到19株活性菌株；二级复筛采用牛津杯定量扩散法，得到5株优良菌株。对优良菌株GX-21进行鉴定，通过形态特征观察、培养特性观察、生理生化试验和16S rDNA序列分析，确定菌株GX-21为多产色链霉菌（Streptomyces polychromogenes）。菌株GX-21具有抑菌谱广的特点，对革兰氏阳性菌、革兰氏阴性菌和真菌均有抑制作用。

A total of 1026 strains of actinomycetes were isolated from 156 soil samples collected from 11 locations in Guangdong Province and its surrounding areas. Soil was pretreated using enrichment culture method with calcium carbonate, and actinomycetes were isolated by plate dilution method. Gause No. 1 synthetic medium was used as the separation medium with 50 mg/L potassium dichromate as the inhibitor. Preliminary antibacterial screening using agar plug method, with five kinds of indicative bacteria including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Candida albicans, and Aspergillus niger, and 95 active strains were identified. Re-screening consisted of two screening levels with eight kinds of indicative bacteria, including the five used in preliminary screening and Vibrio parahaemolyticus, Pseudomonas aeruginosa, and Proteus vulgaris. The agar plug method used in the first level provided 19 active strains, and the Oxford cup diffusion method in the second level finally provided eight optimal strains. The optimal strain GX-21 was identified as Streptomyces polychromogenes based on morphological and cultural characteristics, physiological and biochemical tests, and 16S rDNA sequence analysis. This strain showed broad-spectrum antimicrobial activity, effective against gram-positive and -negative bacteria and fungi.

广东省重大专项（2010A080403005）；广东省科技计划项目（2012B050800007）