Cotton plug preparation

                                             

Microorganisms are ubiquitous in distribution. In a given habitat, a variety of microorganisms are present at a time. It is rather difficult to study particular type of microbe unless we know their ecological nature. Anaerobic bacteria do not require oxygen while aerobic one requires oxygen. Microaerophilic ones require it in a low concentration. Therefore we need cotton plug to create aerobic environment and to make the growing culture free from undesired microbes. Cotton plugs have cotton fibres and air pores. Air can pass through the pores but not microbial contaminants. They adhere on the surface of cotton fibres and are prevented from entering the flask, tubes etc. 

Materials required 

Nonabsorbent cotton rolls, Culture tubes, flasks, scissors. 

Procedure 

1. The roll of cotton which is non-absorbent is opened as per requirement (ie., number, size, shape) 

2. A small piece of cotton is cut with the help of scissors. Based on the requirement, two types of cotton plugs are prepared. 

A) Cut, Fold & Rolled Plug 

1. A small piece of cotton sheet is cut with the help of scissors as per requirement. 

2. Cut piece is folded from the centre. 

3. The sheet is then rolled from any of the ends opposite to the folded side. 

4. The folded and rolled side is inserted in the mouth of a flask or culture tube and the other end of cotton plug bears cotton fibres that emerge out freely. 

5. If it is tight, the plug is opened and some cotton is removed from one side and readjusted as earlier. 

B) Cut, Rolled & Fold Plug 

1. A small piece of cotton sheet is cut with the help of scissors as per requirement. 

2. The piece is rolled from one end 

3. The rolled piece is then folded from the centre 

4. The folded end is inserted in the mouth of glass or culture tube and the other end bears cotton fibres.