[js1138]

So when a bacterium has errors in gene replication, who gets the mutation, the original organism or the copy?

[Nebullis]

So when a bacterium has errors in gene replication, who gets the mutation, the original organism or the copy?

Normally in the copy. There can be damage or incorrect repair to the original, but normally, even in eukaryotes, replication errors are found in the copy. Pol IV, discussed in the article, makes lots of mismatch errors and doesn't proofread and correct them.