Mucoid strains of Pseudomonas aeruginosa are characterized by an overproduc
tion of the extracellular polysaccharide alginate. When suspended into chlo
rinated swimming-pool water or drinking water samples, mucoid bacteria reve
aled enhanced survival compared with isogenic nonmucoid cells. Removal of s
lime from mucoid bacteria abolished chlorine resistance, addition of purifi
ed alginate to washed bacteria again enhanced survival. Thus, alginate-cont
aining slime confers protection on P. aeruginosa against chlorine and may c
ontribute to survival of these bacteria in chlorinated water systems.