The isolation and comparison of cellulase genes from two strains of Ruminococcus albus

Endo-1,4-beta-glucanase genes have been cloned from two strains of Ruminococcus albus recently isolated in this laboratory. Although the strains were phenotypically similar, cross-hybridization studies between them showed significant genetic differences, with only 20% of the genome forming DNA heteroduplexes. Heteroduplexes displayed an average dissociation temperature 9 degrees C lower than that of the homoduplex. Consistent with this, restriction maps of the two endoglucanase genes showed no similarity, and hybridization work using the endoglucanase genes as probes revealed that neither gene was present in the genome of the other isolate of R. albus. Comparative enzyme characterization showed differences between the enzymes in their response to temperature, pH and substrate preference.