The term "bacteria" is already the collective name for this group of microorganisms. It's like asking what a "cat" is called!

However, if you're asking about specific types of bacteria, you might be looking for:

* Species names: Like *Escherichia coli* or *Staphylococcus aureus*.

* Groups or classifications: Like gram-positive bacteria, or nitrogen-fixing bacteria.

* Informal names: Like "good bacteria" (referring to probiotics) or "bad bacteria" (referring to pathogens).

Could you tell me what you're interested in knowing more about? I can help you understand the specific terminology you're looking for.