Objective 1. As reported previously, methyl accepting chemotaxis proteins (MCPs) were identified for wide (Xcc62, Xcc306) and narrow host range strains of Xanthomonas citri subsp. citri (Xcc) compared to X. fuscans subsp. aurantifolii B and C strains, X. alfalfae sbsp. citrumelonis (Xac) or X. campestris pv. campestris (Xc). All Xcc strains showed similar MCP content except Xcc306 which lacked some of the MCPs. MCP analysis was expanded to include Xcc strains from different geographical areas. 37 strains from Argentina (27%), Uruguay (32.5%), Brazil (27%) and 5 isolates from citrus of uncertain origin (13.5%) were analyzed for 15 MCPs. Only one of the MCPs was conserved among all Xanthomonas strains (XCV1951), and two of them were specific of Xc (XCC0324 and XCC1954). Objective 2. The role of extracellular DNA (eDNA) was evaluated in the formation and stabilization of the biofilm matrix. The presence of eDNA in biofilm was confirmed for several Xcc strains and Xac. DNAse treatments of Xcc strains and Xac reduced biofilm formation at the initial stage of development as well as disrupted preformed biofilm. The DNAse effect on formation or disruption varied among Xcc strains and Xanthomonas species and indicates differing roles for eDNA. Differences in fiber structures containing eDNA in biofilms, bacterial cultures, and in twitching motility assays were detected by SYTO-9 staining and fluorescence microscopy. The proposed roles for eDNA in the early stages of biofilm formation are as an adhesin and in mature biofilms as a structural component. .