Diverse genes of cellulase homologues of glycosyl hydrolase family 45 fromthe symbiotic protists in the hindgut of the termite Reticulitermes speratus

Diverse genes encoding cellulase homologues belonging to glycosyl hydrolase family 45 were identified from the symbiotic protists in the hindgut of th e termite Reticulitermes speratus through the use of consensus PCR and the screening of a cDNA library. Fifteen full-length cDNA clones were isolated and sequenced, which encoded polypeptides consisting of 218-221 amino acid residues showing up to 63% identity to known family 45 cellulases. The cell ulase sequences of the termite symbiotic protists were phylogenetically mon ophyletic, showing more than 75% amino acid identity with each other. These enzymes consist of a single catalytic domain, lacking the ancillary domain s found in most microbial cellulases. By whole-cell in situ hybridization u sing oligonucleotide probes specific for regions conserved in some of the s equences, the origin of the genes was identified as symbiotic hypermastigot e protists. The presence of diverse cellulase homologues suggests that symb iotic protists of termites may be rich reservoirs of novel cellulase sequen ces.