bead beating - (Feb/19/2008 )

Hi ,
I would like to extract DNA from a very small amount of bacteria[=> total end-volume (including a lysis buffer) is 50ul] using glass beads.
Does any of you know which amount of beads should I use in this situation?

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What is really important is to mention where you would like to extract bacteria from? (soil, culture, tissue, etc)

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Hi,
Thank you for your reply. There are only bacteria (derived from soil, very small quantities, I assume) resuspended in water (25ul), there are no soil particles and anything else. I add 25 ul of a buffer and want to use also bead bitting step afterwards. But as I said, I do not know how much of these I should add.
I have found that the bead diameter of 0.1 mm is usually used and for 0.5g of soil, 0.5g of beads is used (ratio 1:1). But what should I do if I do not have soil in my sample? Should I use double amount of beads?
Thanks for any response:)

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In our lab we use the Griffiths method for this type of extraction (Griffiths et al. (2000) Appl & Environ Microbiol. 66, 5488-5491). We are using a 1 : 1 : 1 : 1 ratio of soil beads, buffer and phenol chloroform isoamyl alcohol. For beads we combine I think (I can check the sizes) 0.2g of 50 - 70um sand and 0.3g of ~0.5mm glass beads. I don't think, however, you will have any problem with using only 0.5g 0.1mm glass beads.

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Dear Odiporos ,
Thank you very much. You've helped me a lot.
K.

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