β-Glucosidase Activity in Phytopathogenic Bacteria

Most of 58 isolates of phytopathogenic and related bacteria comprising 24 species in the genera Agrobacterium, Erwinia, Corynebacterium, Pseudomonas, and Xanthomonas exhibited beta-glucosidase activity, especially the gall-nonforming pathogenic pseudomonads and soft rot organisms. The gall-forming pseudomonads and P. fluorescens exhibited no beta-glucosidase activity, with the exception of one isolate of P. savastanoi which showed slight activity on an inorganic nitrogen-arbutin medium. The best medium for demonstrating beta-glucosidase activity contained peptone as the nitrogen source and arbutin. beta-Glucosidase activity in this medium was indicated by either acid production or browning. P. syringae, in contrast to other bacteria tested, produced most beta-glucosidase in a medium containing large amounts of glucose. Chromatographic analyses confirmed that splitting of the glucoside occurred at the glucosidic linkage. Reaction of sonically treated bacterial cells with indican or p-nitrophenyl-beta-D-glucoside proved a rapid method for assaying relative amounts of beta-glucosidase among bacterial species. Harda's paper-strip method of detecting beta-glucosidase also was useful in revealing the distribution and relative amounts of beta-glucosidase in most bacteria, but did not indicate the relatively greater amount of beta-glucosidase in P. syringae.