I just had this site pointed out to me by Merry Youle.
This site is a collection of audio and video of lectures that were for the "Microbes, Minerals, and the Environment" symposium. The collection includes talks by David Stahl, Derek Lovely, Anna Louise Reysenbach, Faroq Azam, Jonathan Zehr, and Paul Falkowski, all relating to microbes in the enviornonment. I have not watched all of them but the ones I have seen are quite good.
The symposium was in honor of Philip Abelson, who died in 2004.