Final answer:
The periplasmic space is found in Gram-negative bacteria between the thin peptidoglycan wall and the outer membrane. Gram-positive bacteria do not have this space as their cell walls are thick and directly anchored to the cytoplasmic membrane by lipoteichoic acid.
Step-by-step explanation:
The periplasmic space is a characteristic feature present in Gram-negative bacteria. In these bacteria, this space is found between the thin peptidoglycan cell wall and the outer membrane. Gram-positive bacteria, on the other hand, have a thick peptidoglycan layer and lack the outer membrane and periplasmic space.
Gram-negative bacteria possess an additional outer membrane containing lipopolysaccharides and proteins like porins, which allow substances to pass through. This outer membrane is what characterizes the Gram-negative bacteria and differentiates them from Gram-positive bacteria. The lipoteichoic acid present in Gram-positive bacteria anchors the peptidoglycan cell wall directly to the cytoplasmic membrane without the presence of a periplasmic space.