Water supplies are treated with chlorine to kill pathogens. chlorine reacts well with many other chemicals and bacterial cells because it is a strong oxidant. however, legionella pneumophila can sometimes evade killing by residual chlorine. how does it do this? view available hint(s) water supplies are treated with chlorine to kill pathogens. chlorine reacts well with many other chemicals and bacterial cells because it is a strong oxidant. however, legionella pneumophila can sometimes evade killing by residual chlorine. how does it do this? legionella can detoxify chlorine by metabolizing it. legionella produces cations that bind up the negative chloride ions, thus inactivating them. legionella tends to be found in warm waters and in aerosols, both situations in which the chlorine readily evaporates and, thus, is in lower concentration in the water. legionella tends to form biofilms and infect other microbial cells as intracellular pathogens.