FIG. 4.

(A) Hypothetical model for chitin utilization in X. fastidiosa. Chitin is hydrolyzed to chitobiose outside the cell by chiA and passively transported into the periplasmic space as a dimer. nahA converts the substrate into N-acetylglucosamine, which is phosphorylated and transported into the cytoplasm via an ABC transporter. (B) Scanning electron microscopy micrograph of X. fastidiosa cells colonizing the mouthparts of a leafhopper vector. The arrows indicate potential degradation of the chitinous surface at the fringe of the microcolony. The picture is an unpublished image obtained in a previous study (2).