Do all bacterial cells have a double membrane?

Question

I’m reading that gram positive and negative bacteria have an inner plasma membrane surrounding the cytoplasm, then a periplasmic space, then an outer membrane. \nHow does this compare to my general knowledge of bacterial cells having one plasma membrane surrounded by a cell wall?!\n

Answer 1

The outer "membrane" is the cell wall, made of lipopolysaccharide and protein, and is not a lipid bilayer. All living organisms have a cell membrane (lipid bilayer) but only bacteria, fungi, and plants have a cell wall. Gram positive bacteria have multilayered peptidoglycan and retain crystal violet stain (blue) whereas gram negative bacterial have a single layer of peptidoglycan and do not retain crystal violet.