Final answer:
Gram-negative bacteria have a unique double layer outer cell membrane which includes an outer envelope with lipopolysaccharides and lipoproteins.
Step-by-step explanation:
Bacteria which have a double layer outer cell membrane are called gram-negative bacteria. These types of bacteria have a relatively thin cell wall composed of a few layers of peptidoglycan, accounting for only about 10 percent of their total cell wall structure. This cell wall is encompassed by an outer envelope containing lipopolysaccharides (LPS) and lipoproteins, distinguishing them from gram-positive bacteria, which have a thick peptidoglycan cell wall and lack this outer membrane. The presence of this outer membrane in gram-negative bacteria can affect the treatment of bacterial infections, as it can offer resistance to certain antibiotics through mechanisms like the efflux pumps.