Freeze drying prior to DNA extraction - (Mar/23/2010 )

I'm going to be extracting bacterial community DNA from a marine sponge. A method that I am thinking of persuing is that the sponge samples should be freeze-dried, then homogenised while being cooled by liquid nitrogen to form a powder. The powder then undergoes the DNA extraction process.

My question is what does that freeze drying step acheive? Can the samples be homogenised while frozen without drying or would this cause damage to the bacterial cells that may effect the DNA?

Cheers
M

I think either way would work. The frozen material will almost certainly thaw during homogenization, so enzymes could be active then, but I don't think this is a major issue for early stages of a bacterial sample prep.