Isolation and characterization of novel cellulase genes from uncultured microorganisms in different environmental niches

Abstract

Four different environmental DNA libraries were prepared from microbial consortium collected from forest soil, dung of elephant, cow rumen and rotted tree. Seven independent clones specifying cellulase activities (five endo-beta-1,4-glucanases and two beta-glucosidases) were isolated and identified. Sequence analysis of the retrieved genes revealed that the encoded products of these cellulase genes shared less than 50% identities and 70% similarities to cellulases in the databases. Domain analysis predicted that four endo-beta-1,4-glucanases conform to glycolsyl hydrolase family 5 (GHF 5) and one endo-beta-1,4-glucanase to glycolsyl hydrolase family 9 (GHF 9), while both beta-glucosidases belong to glycolsyl hydrolase family 3 (GHF 3). Further sequence analysis indicated that although a solid affiliation could be made for the two endo-beta-1,4-glucanases to the typical ruminal microbe Prevotella ruminicola, the rest formed deep-branched lineages with no close relatives. The revelation of the phylogenetic novelty provided a snapshot on the great diversity of cellulases in these natural environments.

Identification and Characterization of a Cellulase-Encoding Gene from the Buffalo Rumen Metagenomic Library

“…Compared to other endocellulases, BT-01 exhibited endocellulase activity in the range of those shown by other cellulases belonging to GHF5. 7,13,44) The high activity of BT-01 toward -glucan is advantageous. Since most ingredients in feedstuffs, such as soybean and corn meal, contain NSPs that are high in -glucan, BT-01 is most suitable for utilization as a feed additive.…”

Mining metagenomes for novel cellulase genes

“…The rumen is the most potent fiber fermentation system. Microbes play an essential role in degrading cellulosic materials of plants in the rumen, which represents a potentially important resource of cellulases, and several metagenomic studies focused on this environment Ferrer et al 2005;Liu et al 2009;Palackal et al 2007;Shedova et al 2009;Wang et al 2009). Ferrer et al (2005) constructed a metagenomic expression library from the contents of the cow rumen and screened it for cellulase activities, which resulted in the recovery of seven clones encoding b-1,4-endoglucanase activity.…”

Multisubstrate Isotope Labeling and Metagenomic Analysis of Active Soil Bacterial Communities

“…Given that metagenomic studies demonstrate that the majority of total genetic diversity space remains unexplored, “it will be far more efficient and productive to seek new enzymes from metagenome libraries than to tweak the activities of existing ones” (10). Indeed, there are several recent examples of GHs (e.g., cellulases) recovered by functional screening of metagenomic libraries from terrestrial environments (e.g., see references 11, 12, 13, and 14). These studies reflect a laborious limitation of bulk DNA metagenomic library construction: in the absence of suitable selections for phenotype, many clones (e.g., tens of thousands) must be screened prior to recovering targets of interest.…”