Agar is used for solidifying culture media.

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Both of these are solid at room temperature.Think about Jello melting in the summer heat if you think about Gelatin melting at a relatively low temperature.Agar is melting at 85 degrees.When agar is put into a petri dish, it will likely melt or at least not be as firm, as the bacterium will end up in a soupy mess.Agar can be hard to digest bybacteria.

Agar will stay solid at higher temperatures.The media won't start to liquefy if you stick your plates in an incubator or if a lab mate likes the warm side.We can thank Walther and his wife.During the summer he would have problems with media plates because they would start to melt.His wife's jams were able to last through the summer.He asked her how she was able to do this, and she said she had begun using agar.Agar was used in plate making.257-265.If you would like to see the story, I included a link to the pages from the books.

Koch and his laboratory were constantly frustrated by the lack of a good solid medium because potatoes failed to support the growth of many microorganisms.Walter Hesse joined Koch's laboratory to do studies on air quality, showing a remarkable attention to detail and patience in his work.His wife, who is also raising their three sons, would assist her husband with his research in the laboratory.Walter was trying to do his air quality experiments using a solidifying agent.The solidifying agent would be used when the temperatures rise above the melting point.In both cases, the liquefaction of the medium would ruin the experiments because the cultures that were capable of degrading gelatin would grow in them.One day while eating lunch, the frustrated scientist asked why her puddings stayed solid even in the hot summer temperatures.She told him about agar-agar, a heat resistant gelling agent that she had learned about while growing up in New York.