Gram-negative bacteria are more harmful than gram-positive bacteria. This is because gram-negative bacteria have a hard, protective outer shell, which makes them more resistant to antibiotics and hence harder to kill. Moreover, when the cell wall is disturbed, gram-negative bacteria release endotoxins that can exacerbate existing symptoms. With their higher resistance to antibiotics, gram-negative bacteria cause significant morbidity and mortality, making them considerably more harmful than gram-positive bacteria.