Debbie Knight

Photo of the week

In photo log on February 28, 2012 at 9:00 am

This is a photo of agar plates used to grow bacteria.

Powdered bacterial medium is measured out and water is added. To make the medium in the petri dishes “gel” (like Jell-O), a material called “agar” is also added to the mix. In the lab, agar starts out as a powdered substance but melts when heated to a boil. As it cools, it “solidifies” or “gels” to something a little firmer than Jell-O at the concentration we use it.

In the photo, the boiled (sterilized) medium in the flask is on the left — it is still a liquid. Some of that liquid was poured into the petri dishes on the right. As the medium cools in those dishes, it will become a food source for cultured bacteria as well as provide a solid surface for their growth. It usually takes a couple of hours for the plates to “set.” After which they can be stored in the refrigerator for about a month before they are used in experiments.

  1. I love these posts. Short and very educational about #lifeinthelab. I’m still waiting for a freezer pic. 🙂 (unless I missed while on honeymoon). The difference between an organized freezer and messy one can be $1000’s of misidentified/misplaced samples, costing tax payers.

    Is there a way for you to group all your photo of the week pics into one folder? So they are easier to find?

    Thank you, Good work Deb.

    • Thanks, Tom. As for your fascination about freezers, I did post a picture of my old lab’s freezers in a previous post in July: Lesson for scientists? Don’t throw away any of your experimental samples! I will work on getting you a picture of my current lab’s freezer space. I try to keep them pretty organized.

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