Question

why eubacteria is also known as true bacteria

Answer 1

Actually Eubacteria is the other name for true bacteria.
"Eu" means true.
There are basically two types of bacteria --
1) Archaebacteria
2) Eubacteria

While eubacteria are true bacteria , Archaebacteria means ancient bacteria.
To distinguish between the ancient and new bacteria , they have been classified into true and ancient bacteria.

Answer 2

Eu in Latin means true bacteria
So eubacteria means truebacteria