Application of Congo Red Staining in Fully Automatic Biological Tissue Staining Machine

The fully automatic biological tissue staining machine is mainly used for staining some biological tissues. Below, I will introduce the advantages and disadvantages of two Congo red staining methods.

There are two commonly used Congo red staining methods. One is to first cultivate microorganisms and then add Congo red for color reaction, and the other is to add Congo red when pouring the plate.

Method 1: Cover the culture medium with a CR solution with a mass concentration of 1 mg/mI. After 10-15 minutes, remove the CR solution and add a NaCI solution with a mass concentration of 1 mol/I. After 15 minutes, remove the NaCl solution. At this point, a transparent circle will appear around the cellulase producing colonies.

Method 2: Prepare a CR solution with a mass concentration of 10mg/mI. After sterilization, add 1mI of CR solution to every 200mL of culture medium, mix well, and then pour the plate. When bacteria grow on the culture medium, there will be a clear transparent circle around the colony that produces cellulase.

The comparison of two Congo red staining methods: Congo red has been used for screening cellulose degrading bacteria for over 20 years, and two methods are provided in textbooks.

Method 1: It is a traditional method, but the disadvantage is that the operation is cumbersome, and adding Congo red solution can cause mixing between colonies; The advantage is that the color reaction displayed in this way is essentially the action of cellulose decomposing bacteria.

Method 2: The advantage is that it is easy to operate and there is no problem of mixed colonies. The disadvantage is that starch substances are contained in cellulose powder, agar, and potato juice, which can cause false positive reactions of microorganisms that can produce amylase. However, the transparent circles produced by microorganisms that only produce amylase are relatively blurry, as cellulose dominates the culture medium and can be distinguished from the transparent circles produced by cellulase. Another disadvantage of Method 2 is that some microorganisms have the ability to degrade pigments, and during long-term cultivation, they will degrade Congo red to form clear transparent circles, which are difficult to distinguish from cellulose degrading bacteria.