从4个不同地区土样中共分离得到20株天然无抗菌活性或抗菌活性微弱放线菌,采用链霉素(Streptomycin)、庆大霉素(Gentamycin)及利福平(Rifampicin)三重抗性法对其进行活性菌株的筛选后,17株放线菌的发酵液显示了抑菌活性,其中1号放线菌对链霉素、庆大霉素和利福平抗性分别为40、10和150 g·mL-1,其发酵液对枯草芽孢杆菌ATCC 6633(Bacillus subtilis)及藤黄微球菌ATCC 9341(Micrococcus luteus)的抑菌圈直径分别为20.52和23.23mm,均高于其他放线菌.对其发酵液中活性物质的温度及酸碱度稳定性测定结果显示,该放线菌的发酵液上清在50℃水浴条件下处理1 h后,其抑菌活性基本丧失,而pH小于4或大于9的酸碱度处理也都会使其失活;相反,菌体浸提液经过90 ℃水浴1.5 h以及pH达到2和11的处理后其活性仍然稳定.根据形态观察,16S rDNA序列测定,初步确定该放线菌属于链霉菌属(Streptomyces).%In this work, 17 strains showed the bioactivity against tested bacteria were screened out from 20 actinomycetes with poor or without antimicrobial activity isolated from several soil samples after the treatment of three kinds of antibiotics (streptomycin, gentamicin and rifampicin). Among these strains, No. 1 actinomycete strain exhibited the highest antimicrobial activity against Bacillus subtilis ATCC 6633 and Micrococcus luteus ATCC 9341 with a inhibition zone of 20.52 and 23.23 mm,respectively, and possessed the resistant levels of 40, 10 and 150 μg· mL-1 to streptomycin, gentamicin and rifampicin, respectively. The sensitivities of the secondary metabolites to temperature and acidity-alkalinity were evaluated. The results demonstrated that antibacterial activities were almost disappeared when the supernatant was processed under 50 ℃ for 1 h, and significantly reduced after exposure to acidic or basic condition (pH＜4 or ＞9). However, the antibacterial activities of the mycelium extract remained almost unchanged when it was held at 90 ℃ for 1.5 h or exposed to conditions in the pH range 2-11. This actinomycete strain was identified as Streptomyces based on its morphological and physiological properties as well as 16S rDNA sequence analysis.
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