Final answer:
The Gram-positive cell wall gets its negative charge from teichoic acids, which are acidic substances found in the cell wall. Teichoic acids are composed of peptidoglycan, which is the main component of the cell wall in Gram-positive bacteria.
Step-by-step explanation:
The Gram-positive cell wall gets its negative charge from teichoic acids, which are acidic substances found in the cell wall. Up to 90 percent of the Gram-positive bacteria's cell wall is composed of peptidoglycan, and most of the remaining percentage is made up of teichoic acids. These teichoic acids may also be covalently linked to lipids in the plasma membrane to form lipoteichoic acids, which further anchor the cell wall to the cell membrane.