Field of Science

How our lab neighbors melt their agar media


Each bottle on its own heater-stirrer, with its own stir-bar, stirring gently and slowly melting from the bottom up.  Don't these people have a microwave oven?


  1. Seems like a great way to get an explosion, if they manage to get the bottom to boil just a little before the top is melted.

  2. The heat is quite low. But one time they forgot a bottle over the weekend. It was thoroughly cooked when I discovered it.

  3. How do they get the stir-bar to the bottom of the bottle? Do they put a new stir-bar into each bottle before they autoclave it?

  4. I guess they add a stir-bar to each bottle with the medium, before it's autoclaved.

  5. Hello

    I have been in into the idea that is not a good choice to use de microwave oven to melt media, since this could damage the media components, and then interfere with the growing in the culture plates or tubes. Is this a true or false?

    1. In principle it's possible that the molecular vibrations induced by microwaves would affect some molecular reaction differently than the vibrations induced by direct heating. But it seems very unlikely that the nutritional properties of the medium would be altered, and I've certainly never heard of any evidence for this.

  6. Hello again,

    As I recall, the media should be melted not even in a heat plate directly, but in a bath water, so the heating is evenly distributed and there is no risk of overheating the media, it could also be used a heat plate, but it is needed a magnetic stir-bar, so an efficient distribution of the heat can be achieved and yes, a stir-bar is needed for each flask. The microwave use is discouraged not because it could damage the nutritional components of the media, but because it is more easily the media could be overheated, and then by means of the Maillard reaction, several anti-nutritional compounds may be formed, and these compounds even in small quantities may partially inhibit the microorganisms growth, specially in dedicated microorganisms. The microwave can be used heating the media for small periods, until the media is melted, so accidental overheated is avoided. Of course with some practice, people get to "know" their usual media and the microwave potency, so overheating it not a problem, but with new personal, it can be fairly common, so, heating in a water bath is considered as a good laboratory practice, despise being more slow o laborious.

  7. That was us. We were afraid of making a mess in the microwave. Then we almost burned down the lab. Sorry! We'll try not to.

    -Misguided Undergrad


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