Fragen über die Beispielsätze mit, und die Definition und Benutzung von "Cultured"

A: Bacterium relates to bacteria, or germs. Basically, it's a "clever" that is saying that the receiver of the insult is uncultured.
What that means may depend on the context: it could mean that you don't know much about popular things (or, at least, things that the speaker thinks are common knowledge), or it could mean that they think you're careless or slovenly (rude, careless, unprofessional, ect.), or it could be simply a general insult.
While it is supposed to be insulting, many friends say these sorts of things to each other in a playful way, teasing each other. So, it's not necessarily mean, depending on the context. However, you don't want to say something like this to someone, unless you are close with them and know that they won't mind.
I hope this helps, have a nice day!

A: Yes.

Cultured = having refined taste and manners, and a good education

More info: https://www.vocabulary.com/dictionary/cultured

A: The tone of voice is deep. Cultured means they speak clearly, use complex sentences, have a large vocabulary and are thoughtful in how they speak. Patrick Stewart, Morgan Freeman are examples of cultured voices.