vi GENERAL LABORATORY RULES ONCULTURE MEDIA AND CULTURE MEDIA PREPARATION1. Store sealed or unopened culture media containers in a dry atmosphere at about 15-20 oC. Recap/seal properly and immediately opened culture media bottles after use. Dehydrated culture media are hygroscopic in nature and are sensitive to moisture, heat and light. Discard the medium if the powder is not free-flowing, if the color has changed and/or if it looks abnormal. 2. It is best to use calibrated equipment for media preparation such as a weighing scale, analytical balance, pH meter, etc. 3. Prepare a complete list of needed media, chemicals and reagents. All computations for media preparation should be made prior to entering the weighing area. Weigh only the amounts needed. In general, prepare only for a week’s requirement.4. Wear gloves and mask preferably while preparing media, especially for selective media with toxic ingredients (e.g. sodium azide, thallium salts, etc.). The gloves and mask also afford protection against prolonged contact of the media/chemical with the skin and inhalation of media dust or powder during weighing, respectively.