[TorrnT]

To explain how the bacteria arrived in the first place would give away the ending of the short story (which is meant to be a surprise). Although it would not be hard to figure out now, since all the clues are available. The bacteria was a man made strain created to bypass the reptile/theropod stage.
Remember time travel is involved, this leads to the paradox of how life started. I have only placed parts of the story/plot (as to tell all would ruin it) But I wanted to do a larger twist on which came first, "the chicken or the egg", (a scientific mind would say egg) with time travel added, the survival of a race v the survival of many, and a meteor set on a collision course for earth, (before humans had evolved). The trial and error (the earth had many extinctions) Believe me it all ties together in the end, how believable it is.... well the whole story would have to be written and read.

(spoiler)********(the earth was a test bed)

This is how it would have happened had had the earth been allowed to follow its course naturally.
Amino acids and electrical charges of minute quantity causes chain reactions, in a chemical soup. DNA and RNA, both made of amino acids and develop in chains, this is to close of a connection to leave unstudied, which scientists are presently doing. (and no connection to the short story other than the use of DNA and RNA)