CELL-BOUND CELLULASE AND POLYGALACTURONASE PRODUCTION BY RHIZOBIUM AND BRADYRHIZOBIUM SPECIES

Carboxymethyl cellulase and polygalacturonase activities were evaluate d in wild-type strains from different taxonomic groups of rhizobia whi ch nodulate a specific range of legume hosts that do not normally over lap (R. meliloti, R. loti, R. leguminosarum biovar trifolii, R. legumi nosarum biovar phaseoli, R. leguminosarum biovar viceae, and Bradyrhiz obium japonicum). To detect these enzymatic activities we used various methods. a double-layer plate assay, quantitation of reducing sugar p roducts with a bicinchoninate reagent, and viscometric assay. CM-cellu lase activity was found in extracts from all the rhizobia tested. In c ontrast, polygalacturonase activity was only found in R. leguminosarum biovar trifolii and R. meliloti. CM-cellulase and polygalacturonase e nzymes were cell-bound and not detected in the extracellular culture m edium. CM-cellulase isozymes were examined using activity gel electrop horesis. The results obtained shown a heterogeneity of CM-cellulase is ozymes among the strains tested. These findings are consistent with th e hypothesis of an involvement of rhizobial cellulolytic enzymes in th e invasion of legumes by Rhizobium. Copyright (C) 1996 Elsevier Scienc e Ltd.