Abstract：
Diverse habitats have been screened for novel antimicrobial actinomycetes, while others remain unexplored. In this study, we analyzed the bioactivities of actinomycetes cultured from rhizosphere soils of the desert plant Artemisia tridentata and the nearby bulk soils. Actinomycetes were screened for antifungal and antibacterial activities toward a panel of plant pathogens; all comparisons were between activities of rhizosphere soil isolates toward those of its counterpart bulk soil. A selected group of the strongest antifungal isolates were also tested against two antifungal-drug resistant strains of Candida albicans. 16S rDNA partial sequences and phylogenetic analysis of isolates that showed broad-spectrum antifungal activities were performed. Forty-two out of 200 and two soil isolated actinomycetes were selected for their strong antifungal activities. The highest proportion of isolates (p<0.05) from rhizosphere soil of an old plant showed antagonism against gram-positive bacteria (0.483 and 0.224 proportions against Bacillus subtilis and Rathayibacter tritici, respectively), and phytopathogenic fungi (0.259, 0.431, and 0.345 proportions against Fusarium oxysporum, Rhizoctonia solani and Pythium ultimum, respectively), while the highest antagonism against the gram-negative bacteria predominated in isolates from the bulk soils. Isolates from a rhizosphere soil of a young plant were characterized for strong antagonist activities against Fusarium oxysporum (0.333 proportion, p<0.05). Phylogenetic analysis of 16S rDNA sequences showed that isolates that exhibited strong antifungal activity were genetically similar. We conclude that the rhizosphere soil of A. tridentata is an excellent source for discovery of actinomycetes with potentially novel antifungal compounds.
摘要：
已经筛选了各种栖息地的新型抗菌放线菌，而其他人仍未被探索。在这项研究中,我们分析了从荒漠植物蒿的根际土壤和附近的块状土壤中培养的放线菌的生物活性。筛选了放线菌对一组植物病原体的抗真菌和抗菌活性；所有比较都是在根际土壤分离株对其对应的块状土壤的活性之间进行的。还针对白色念珠菌的两种抗真菌耐药菌株测试了一组最强的抗真菌分离株。对显示广谱抗真菌活性的分离株进行了16SrDNA部分序列和系统发育分析。选择了200个中的42个和两个土壤分离的放线菌，因为它们具有很强的抗真菌活性。来自老植物根际土壤的分离株比例最高（p<0.05）对革兰氏阳性菌具有拮抗作用（对枯草芽孢杆菌和小麦芽孢杆菌的比例为0.483和0.224，分别)，和植物病原真菌（对尖孢镰刀菌的比例为0.259、0.431和0.345，solani根瘤菌和ultimum腐霉，分别)，而对革兰氏阴性菌的最高拮抗作用在散装土壤的分离物中占主导地位。来自幼小植物根际土壤的分离株具有对尖孢镰刀菌的强烈拮抗活性（0.333比例，p<0.05)。16SrDNA序列的系统发育分析表明，表现出强抗真菌活性的分离株在遗传上相似。我们得出的结论是，Tridentata的根际土壤是发现具有潜在新型抗真菌化合物的放线菌的极好来源。
