Electrophoretic mobility of Legionella pneumophila serogroups 1 to 14

Legionella pneumophila (Lp) is ubiquitous in the aquatic environment and can persist within drinking water distribution systems (DWDS) enabling these systems to serve as a potential source of human infections. Bacterial surface charge, deduced from electrophoretic mobility (EPM), is a well-recognized contributor to microorganism mobility, adherence and interactions with their surrounding environment. In this study, the EPM of 32 Lp strains representing serogroup (sg) 1 to 14 were measured, in 9.15 mM KH2PO4 at pH 8, to understand cell surface properties that may influence their occurrence within DWDS. EPM measurements indicated the charge of Lp varied widely between serogroups with five distinct clusters, from least to most negatively charged: (i) sg1 to 3, 5, and 12; (ii) sg6, 8, and 10; (iii) sg9 and 13; (iv) sg7, 11, and 14; and (v) sg4. The EPM of sg1 and 4 strains were pH dependent; however, values were constant between pH 6 and 9, a range typical of drinking water, suggesting that EPM differences between Lp serogroups could impact their survival within DWDS. Understanding the ecological importance of Lp surface properties (e.g. in mobility, colonization, resistance to disinfectants, etc.) within DWDS would aid in mitigation of health risks associated with this water-based pathogen.