Cell Walls

"Most bacteria are covered by a rigid cell wall that defines their shape and maintains their structural integrity. This coat is needed because most bacteria live in liquid whose concentration of salts and other small molecules is much lower than the concentration of these same small molecules inside the bacterial cell. Since water can flow across the bacterial membrane it would rush into the cell, causing the cell to swell and burst. An antibiotic tat impairs the strength of this cell wall will kill the bacterium by causing the bacterium to burst."
Ch 5 RotM