Heterologous hybridization of bacterial DNA to the endoglucanases A and B structural genes celA and celB of Clostridium thermocellum.

DNA from various cellulolytic and non-cellulolytic bacteria was found to hybridize to Clostridium thermocellum NCIB10682 DNA fragments carrying the structural genes celA and celB which code for endoglucanases A and B. Homology to celA was detected in Agrobacterium rhizogenes, Azospirillum brasilense, Bacillus subtilis, Cellulomonas sp., Clostridium stercorarium, Erwinia chrysanthemi, Pseudomonas solanacearum and Streptomyces griseus. Homology to celB was detected only in B. subtilis, C. stercorarium and E. chrysanthemi. No homology to celA or celB was detected in Agrobacterium tumefaciens, Rhizobium japonicum, Rhizobium meliloti, Rhizobium ORS571 and Trichoderma reesei. Hybridization performed with the homologous strain NCIB10682 and with C. thermocellum LQRI suggested that the two strains were identical in terms of cel genes. In addition, it is likely that the C. thermocellum cel genes, whose number is presently estimated to be at least ten, do not belong to a gene family, since heterologous hybridization was observed only to a single small EcoRI or HindIII fragment homologous to celB.