CHARACTERIZATION OF 10 MESOPHILIC CELLULOLYTIC CLOSTRIDIA ISOLATED FROM A MUNICIPAL SOLID-WASTE DIGESTER

By hybridization experiments with three cloned fragments carrying cellulase genes of Clostridium cellulolyticum, we tried to differentiate 10 cellulolytic mesophilic clostridia, isolated from a municipal solid waste digestor. On the basis of hybridization experiments, three major groups were found among the 10 isolates. The two endoglucanase genes, cel CCA and cel CCB of C. celluloyticum, hybridized with nine strains of our isolates, suggesting homology and widespread distribution of these genes. With cel CCA the strain A31 exhibited a different pattern. In contrast to these nine strains, the strain Al 1 was found to share no or very weak homology with these two probes, which indicated that this strain of cellulolytic clostridia possesses nonidentical cellulase complex. None of these new strains hybridized with nif genes, indicating that these clostridia did not appear to be nitrogen-fixing bacteria. With other biochemical characteristics, we found that these bacteria appeared to be different from the presently known mesophilic cellulolytic clostridia.