Which kingdom consists of unicellular prokaryotes whose cell walls are made of peptidoglycan?

• A. Cyanobacteria
• B. Archaebacteria
• C. Monerans
• D. Eubacteria

Answer: (D)

Cell walls with peptidoglycan are a hallmark of true bacteria. Unicellular prokaryotes that have this kind of cell wall belong to the kingdom Eubacteria. Archaebacteria, on the other hand, have different wall materials and typically lack peptidoglycan, so they aren’t in the same group. Monera is an old term that lumped prokaryotes together, but the classification reflected by this question points to Eubacteria as the kingdom. Cyanobacteria are part of this group, so they share the peptidoglycan-containing walls, but the key idea is that the kingdom named here for those cell-wall characteristics is Eubacteria.