The predatory bacterium Bdellovibrio bacteriovorus drills into a prey bacterium and, once inside, digests it. When the predatory bacterium attacks the gram-negative bacterium, what are the first structures penetrated by B. bacteriovorus on its way into the prey's cytoplasm?
A) lipopolysaccharides and plasma membrane
B) fimbriae and peptidoglycan layer
C) peptidoglycan layer and plasma membrane
D) lipopolysaccharides and an outer membrane