Abstract
In this study, we used a culture-independent method based on library construction and sequencing to analyze the genetic diversity of the cellulase and hemicellulase genes of the bacterial community resident in the hindgut of Holotrichia parallela larvae. The results indicate that there is a large, diverse set of bacterial genes encoding lignocellulose hydrolysis enzymes in the hindgut of H. parallela. The total of 101 distinct gene fragments (similarity <95%) of glycosyl hydrolase families including GH2 (24 genes), GH8 (27 genes), GH10 (19 genes), GH11 (14 genes) and GH36 (17 genes) families was retrieved, and certain sequences of GH2 (10.61%), GH8 (3.33%), and GH11 (18.42%) families had <60% identities with known sequences in GenBank, indicating their novelty. Based on phylogenetic analysis, sequences from hemicellulase families were related to enzymes from Bacteroidetes and Firmicutes. Fragments from cellulase family were most associated with the phylum of Proteobacteria. Furthermore, a full-length endo-xylanase gene was obtained, and the enzyme exhibited activity over a broad range of pH levels. Our results indicate that there are large number of cellulolytic and xylanolytic bacteria in the hindgut of H. parallela larvae, and these symbiotic bacteria play an important role in the degradation of roots and other organic matter for the host insect.