I would ask Creationist Guy why he wants evidence for the evolution of bacteria. The theory of evolution developed from the examination and analysis of evidence that actually still exists. The original bacteria evolved so many billions of years ago that no direct evidence of their evolutionary development remains.
Analysis of their genes allows us to reconstruct an bacterial evolutionary tree, but that's about the best we've been able to do so far. If he wants to know specific details like when, where and how, they be lost forever to history. Even if we managed to evolve bacteria from scratch in the lab, that wouldn't mean that it originally happened the same way. It's quite possible that insufficient evidence exists for us to ever tease out how it originally happened.
--Percy
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