Isolation and preliminary characterization of extracellular proteases produced by strains of Xylella fastidiosa from grapevines

Virulent and weakly virulent grape strains of Xylella fastidiosa grew well on PD3 amended with gelatin and produced zones of hydrolysis on this medium, indicating the presence of proteolytic activity. Proteases also were produced in PD3 broth and degraded gelatin, azocasein, and azocoll, Gelatin was the best substrate for the proteases. In addition to using the gelatin assay, native activity and sodium dodecyl sulfate activity gels aided in visualizing and monitoring protease activity. Strain P of X. fastidiosa produced at least two proteases, designated P1 and P2, of 54 and 50 kDa, respectively. Protease activity was most abundant in the 31-60% ammonium sulfate fractions [...]