What holds the Gram-positive cell wall onto the plasma membrane beneath it?

1. Teichoic acids fill most of the Gram-positive wall that peptidoglycan does not. 2. When a teichoic acid is covalently linked to a lipid of the plasma membrane, it becomes a lipoteichoic acid. 3. Lipoteichoic acids anchor the cell wall to the cell membrane, which is the function asked for. 4. Porins sit in the outer membrane of Gram-negative bacteria, a structure Gram-positive cells lack. 5. S-layer proteins occur on the outside of walls in both archaea and bacteria, so they anchor nothing inward. 6. Lipopolysaccharide belongs to the Gram-negative outer envelope, so it is the wrong group entirely. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 22 "Prokaryotes: Bacteria and Archaea", section 22.2 Structure of Prokaryotes_