土壤细菌的分离与纯化

一 教学要求

通过从土壤中分离纯化细菌，初步掌握微 生物 的分离纯化方法和无菌操作技术。

二 实验原理

常用的分离纯化方法

microorganisms exist in nature as mixed populations. However, to study microorganisms in the laboratory we must have them in the form of a pure culture, that is, one in which all organisms are descendants of the same organism.

单细胞挑取法

简易单细胞挑取法

micromanipulator

平板分离法

streak plate method

The most common way of separating bacterial cells on the agar surface to obtain isolated colonies is the streak plate method. It provides a simple and rapid method of diluting the sample by mechanical means. As the loop is streaked across the agar surface, more and more bacteria are rubbed off until individual separated organisms are deposited on the agar. After incubation, the area at the beginning of the streak pattern will show confluent growth, while the area near the end of the pattern should show discrete colonies.

pour plate method

Another method of separating bacteria is the pour plate method. With the pour plate method, the bacteria are mixed with melted agar until evenly distributed and separated throughout the liquid. The melted agar is then poured into an empty plate and allowed to solidify. After incubation, discrete bacterial colonies can then be found growing both on the agar and in the agar.

spread plate method

The spin plate method involves diluting the bacterial sample in tubes of sterile water, saline, or broth. Small samples of the diluted bacteria are then pipetted onto the surface of agar plates. A sterile, bent-glass rod is then used to spread the bacteria evenly over the entire agar surface.