Reference no: EM133360681

Robert Koch was a German doctor practicing in a German-Polish town. A disease called anthrax was causing economic hardship for the townspeople as anthrax caused the death of sheep and cattle. Robert Koch suspected the causative agent was a microorganism. He searched for ways in which to grow and study the organism. When microorganisms are grown on a solid surface, they form colonies, which are groups of cells derived from a parental cell. Many different solid surfaces were used, but few proved to be effective. Koch used sliced potato as a solid surface on which to grow microbes. Although colonies did grow, the microbes soon digested the potato and the surface was no longer solid, but became a slurry.

Koch tried to grow microbes in serum (blood minus the red blood cells). Heated serum would form a solid gel when allowed to cool. This surface had some limitations, so Koch continued to try and find a more suitable solid surface. Koch added gelatin to a defined liquid media, which would solidify when cooled. He poured the media with gelatin in a glass dish, called a petri dish, after Julias Petri, its inventor.

A refinement of the solid-substrate culture was the replacement of gelatin with agar. Agar is a polysaccharide that is derived from red algae. Dutch colonists in Java first used agar as a thickener in jams and jellies. Agar was introduced into the Koch lab by his colleague, Walther Hesse. Agar has some advantages over gelatin in that it remains solid at higher temperatures and it is indigestible by microbes. Thus, colonies can grow on the surface of agar, but the medium itself does not get digested. Agar is still used in microbiology laboratories to grow colonies of microorganisms.

Questions:

1. State the media used to grow colonies in laboratories today.

2. Define the media used today.

3. Explain why the media used today was better than those used previously.

4. Why did Koch continue to search for a suitable solid substrate to grow microorganisms?

5. How did Walther Hesse know that the media he introduced would work?