COMPARATIVE ANALYSES REVEAL A HIGHLY CONSERVED ENDOGLUCANASE IN THE CELLULOLYTIC GENUS FIBROBACTER

An RNA probe complementary to the endoglucanase 3 gene (cel-3) of Fibr obacter succinogenes S85 hybridized to chromosomal DNAs from isolates representing the genetic diversity of the genus, The probe was subsequ ently used to identify putative cel-3-containing clones from genomic l ibraries of representative Fibrobacter isolates, Comparative sequence analyses of the cloned cel-3 genes confirmed that cel-3 is conserved a mong Fibrobacter isolates and that the ancestral cel-3 gene appears to have coevolved with the genus, since the same genealogy was inferred from sequence comparisons of 168 rRNAs and cel-3 genes, Hybridization comparisons using a xylanase gene probe suggested similar conservation of this gene. Together the data indicate that the cellulolytic appara tus is conserved among Fibrobacter isolates and that comparative analy ses of homologous elements of the apparatus from different members, in relationship to the now established phylogeny of the genus, could ser ve to better define the enzymatic basis of fiber digestion in this gen us.