It's not entirely accurate to say bacteria are unable to undergo mitosis. They simply don't undergo mitosis as we understand it in eukaryotic cells. Here's why:

* Bacteria are prokaryotes. They lack a nucleus and other membrane-bound organelles found in eukaryotes. This includes the microtubules and spindle fibers essential for the separation of chromosomes in mitosis.

* Bacteria divide by binary fission. This is a simpler process of cell division where the bacterial DNA replicates and the cell elongates, eventually dividing into two identical daughter cells.

* No nuclear envelope. Because bacteria don't have a nucleus, their DNA is located in a region called the nucleoid. There's no nuclear envelope to break down and reform during division, as seen in mitosis.

In short: Bacteria have their own unique method of cell division, binary fission, which is adapted to their prokaryotic structure and different from the more complex process of mitosis in eukaryotes.