One way to characterize cells is by staining their cell wall. Two common categories of bacteria are called Gram and Gram -. How are these cell types different? A. Gram cells lack cell wall and Gram - have a cell wall. B. Gram cells have a cell wall and Gram - have a no cell wall. C. Gram cells have a thin cell wall and Gram - have a thick cell wall. D. Gram cells have a thick cell wall and Gram - have a thin cell wall.