Final answer:
Gram-positive bacteria have a thick cell wall made of peptidoglycan, while Gram-negative bacteria have a thinner cell wall surrounded by an outer envelope.
Step-by-step explanation:
Gram-positive and Gram-negative environmental bacteria differ in their cell wall structure. Gram-positive bacteria have a thick cell wall composed mainly of peptidoglycan, while Gram-negative bacteria have a thinner cell wall with a few layers of peptidoglycan surrounded by an outer envelope containing lipopolysaccharides (LPS) and lipoproteins. The outer envelope of Gram-negative bacteria is often referred to as a second lipid bilayer and has a different chemical composition from the plasma membranes of cells.