Comparative genomics reveals cellobiose hydrolysis mechanism of Ruminiclostridium thermocellum M3, a cellulosic saccharification bacterium

The cellulosome of was one of the most efficient cellulase systems in nature. However, the product of cellulose degradation by is cellobiose, which leads to the feedback inhibition of cellulosome, and it limits the application in the field of cellulosic biomass consolidated bioprocessing (CBP) industry. In a previous study, M3, which can hydrolyze cellulosic feedstocks into monosaccharides, was isolated from horse manure. In this study, the complete genome of M3 was sequenced and assembled. The genome of M3 was compared with the other to reveal the mechanism of cellulosic saccharification by M3. In addition, we predicted the key genes for the elimination of feedback inhibition of cellobiose in . The results indicated that the whole genome sequence of M3 consisted of 3.6 Mb of chromosomes with a 38.9% of GC%. To be specific, eight gene islands and 271 carbohydrate-active enzyme-encoded proteins were detected. Moreover, the results of gene function annotation showed that 2,071, 2,120, and 1,246 genes were annotated into the Clusters of Orthologous Groups (COG), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, respectively, and most of the genes were involved in carbohydrate metabolism and enzymatic catalysis. Different from other , strain M3 has three proteins related to β-glucosidase, and the cellobiose hydrolysis was enhanced by the synergy of gene and . Meanwhile, the GH42 family, CBM36 family, and AA8 family might participate in cellobiose degradation.