There are no special problems with large organisms, and for microorganisms, their characters are often difficult to distinguish with the naked eye. Therefore, a simple and easy method is plate culture, that is, the pure strains obtained from plate culture colonies are identified and screened one by one. However, for the antagonistic system, it is necessary to use a selective medium containing drugs and phages when screening. Sometimes the operation is often more complicated than the above according to the different characters selected. Photocopying method is applied as a subtle and ingenious method. Through the statistical analysis of this method and its results, it has been determined that the resistance obtained by adapting to resistant substances and the phenomenon that the requirements for conditions in gene expression are not suitable for normal living environment can be explained by mutation and selective proliferation, and it is considered that mutation has nothing to do with the given adaptation conditions.