Types of Agar

I’ve been doing some research into the types of agar that you can use, as I have become aware that we need to decide soon so that it can be ordered. At the moment we are using MacConkey Agar to grow our bacteria upon, which seems to be working really well – we are able to use clear agar or a red dye – we are wondering what colours may be available. I found this table online, which has helped me understand:

Screen Shot 2013-03-25 at 19.35.37Screen Shot 2013-03-25 at 19.36.18

In this I see that MacConkey only allows ‘gram-negative’ bacteria to grow, I wasn’t sure what this was, but after research I now know it means bacteria that do not retain the violet dye in the Gram Staining protocol. We have practiced this procedure and I will post a blog entry about it soon. Gram negative bacteria do not take up the stain due to the existence of an outer membrane preventing the penetration of the stain, this is shown in the diagram below:

Gram_negative_cell_wall.svg

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