Topic 2: Cultivation of Bacteria

Bacteria must be grown on culture media in order to characterize and identify.

Bacteria require sources of energy, carbon, nitrogen, minerals, and growth factors

Most bacteria are chemoheterotrophs

• require organic compounds for carbon and energy sources

Bacteria exhibit a wide range of nutritional requirements, need enriching nutrients

• milk, serum, blood, tomato juice

Growth factors: organic compounds such as vitamins or amino acids that are incorporated into a cell without alteration

First bacterial cultures were grown in broth/liquid media - infusions and blood

Robert Koch attempted to culture bacteria on potato slices when he realized need for solid media.

• Added gelatin to liquid media when some bacteria wouldn’t grow on potato → however, gelatin liqueified under incubation conditons

• Angelina Hess suggested use of agar as solidfying agent

• Today, agar is the most commonly used solidifying agent in culture media

Aseptic technique is used in microbiology to exclude contaminants

• prevention of unwanted microorganisms in laboratory and medical procedures