Question

if you suspect a contaminant in one of your different media tubes (slant/deep/broth), what should you do to confirm that there is a contaminant?

Answer 1

Pure cultures are prepared by using agar slants, deep cultures and broth cultures. A pure culture contains only one type of bacteria and is different from mixed culture that contains more than 1 type of bacterium. Contamination is process of growth of bacteria than the required pure culture. Contamination is possible when sufficient measures are not followed. For example, heating the inoculum loop or culture test tube with flame are some measures that prevent contamination.

Contamination is suspected or identified when the culture grown in media exhibits different color or different types of growth characteristics. In such cases, the culture is immediated plated by streak or spread plating method. The culture is observed under microscope after incubation and growth. To observe under microscope the culture is stained by Gram staining or special staining methods. For example, spore staining is used for spore forming bacteria.