It is plausible that expression of these enzymes is DSF-dependent. If so, a DSF mutant might densely populate xylem vessels, causing enhanced symptoms because it is unable to traverse the
pit membrane [55].
Fastidium exopolysaccharide is an important virulence factor for Xf. Bacteria attach to xylem
vessels in the absence of the exopolysaccharide, while matrix-encased bacteria appear mainly in densely colonized vessels.
Leite and co-workers proposed an adhesion model in which cell surface-exposed thiol groups associated with membrane features, impart a net negative cell surface charge, promoting divalent ion bridging for bacteria-to-bacteria and bacteria-to-host cell adhesion. The same group found that artificial media based on xylem chemistry stimulates Xf biofilm formation