Final answer:
The key difference between Gram-positive and Gram-negative bacteria is in their cell wall structure, where Gram-positive bacteria have a thick peptidoglycan layer without an outer membrane, while Gram-negative bacteria have a thinner peptidoglycan layer and an additional outer membrane.
Step-by-step explanation:
The only real difference between Gram (+) and Gram (-) bacteria is not the static charge on the cell, shape of the cell, presence of a cell wall, or the ability to produce spores. The true difference lies in their cell wall structure during Gram staining. Gram-positive bacteria have a thick cell wall composed predominantly of peptidoglycan and teichoic acids without an outer membrane. On the other hand, Gram-negative bacteria possess a thinner peptidoglycan layer and have an additional outer membrane containing lipopolysaccharides and lipoproteins which is sometimes referred to as a second lipid bilayer.
Additionally, differences in cellular morphology, such as endospores in Gram-positive bacilli, can be observed with specific staining methods like the endospore stain. However, these are secondary characteristics and not the fundamental distinguishing feature between the two groups.