The influence of carbon source and calcium on the production of proteases by Erwinia chrysanthemi
Erwinia chrysanthemi (Ec) is the causative agent of soft rot diseases in many plants. In order to cause disease, it produces hydrolytic enzymes, which are involved in the degradation of plant tissue. However, the role of proteases in its pathogenicity to plants is not well understood. E. chrysanthemi targets the host’s middle lamella, which was mainly made of pectic substances containing calcium, for colonization. In this study, it is reported that a pectic substance, such as sodium polypectate (NaPP) may be preferable, not only for the production of hydrolytic enzymes, but for the production of protease as well. Furthermore, since the middle lamella contains high levels of calcium, it was thought that it may play an important role in the production of proteases by this organism. Both predictions were supported by the results presented in this study. When E. chrysanthemi subsp. chrysanthemi (Ecc) was grown in HXC medium supplemented with NaPP and calcium, it produced the highest levels of protease as compared to NaPP alone. These results suggest that proteases produced by E. chrysanthemi may be induced in part by calcium.
Key words: Erwinia chrysanthemi, protease, phytopathogenicity, extracellular enzyme.