While the vast majority of bacteria do have cell walls, there are a few exceptions:

* Mycoplasmas: These are a group of bacteria that lack a cell wall. They are often referred to as "wall-less bacteria" and are known for their ability to survive in harsh environments.

* L-forms: These are bacteria that have lost their cell wall due to environmental stress or genetic mutations. They can revert to their original walled state under certain conditions.

Therefore, while cell walls are a common feature of bacteria, their absence is not unheard of.