放线菌是抗菌素产生茵最多的一类微生物,研究其生态分布和拮抗性能,对寻找抗菌素资源有重要意义。放线菌在土壤中数量多,繁殖快。但不同自然条件,不同土类,放线菌的组成和分布也有一定差异,这方面前人已做了许多工作。本文仅对西北黄土区几种主要土类,在不同利用条件下,放线菌的组成、分布和拮抗性能作一初步研究,现报导如下: 一、材料和方法 1978年5～8月份,分别从陕西省的武功、洛川、延安、安塞、详县、关山和甘肃省的子午岭等地采集了(土篓)土、黑垆土、山地棕壤、山地灰褐土、山地褐土等土类的不同发生层次70余份土样。采集后用冰箱保存,两周内分析完毕。分离培养基采用高氏Ⅰ号、高氏Ⅳ号、酪素琼脂、黄豆饼粉浸汁琼脂。用表面涂抹法, Actinomycetes is a kind of microorganism with the largest number of antibiotics, and its ecological distribution and antagonistic properties are very important to find the resources of antibiotics. Actinomycetes in the soil in the number of fast propagation. But different natural conditions, different soil types, composition and distribution of actinomycetes there are some differences, in this regard, many people have done a lot of work. In this paper, only a few of the main loess areas in Northwest China under different conditions, actinomycetes composition, distribution and antagonistic properties for a preliminary study, are reported as follows: First, materials and methods 1978 May to August, respectively (Soil), black mulch soil, mountain brown soil, mountainous gray cinnamon, mountainous cinnamon soil were collected from Wugong, Luochuan, Yan’an, Ansai, Xianxian, Guanshan and Ziwu Mountains in Gansu Province Soil and other soil layers of more than 70 different soil samples. After the collection with the refrigerator to save, analysis within two weeks is completed. Isolation medium using high I, Gao IV, casein agar, soy flour cake dipping agar. With the surface smear method,