Complete genome sequence of Rhodothermaceae bacterium RA with cellulolytic and xylanolytic activities

Abstract

Rhodothermaceae bacterium RA is a halo-thermophile isolated from a saline hot spring. Previously, the genome of this bacterium was sequenced using a HiSeq 2500 platform culminating in 91 contigs. In this report, we report on the resequencing of its complete genome using a PacBio RSII platform. The genome has a GC content of 68.3%, is 4,653,222 bp in size, and encodes 3711 genes. We are interested in understanding the carbohydrate metabolic pathway, in particular the lignocellulosic biomass degradation pathway. Strain RA harbors 57 glycosyl hydrolase (GH) genes that are affiliated with 30 families. The bacterium consists of cellulose-acting (GH 3, 5, 9, and 44) and hemicellulose-acting enzymes (GH 3, 10, and 43). A crude cell-free extract of the bacterium exhibited endoglucanase, xylanase, β-glucosidase, and β-xylosidase activities. The complete genome information coupled with biochemical assays confirms that strain RA is able to degrade cellulose and xylan. Therefore, strain RA is another excellent member of family Rhodothermaceae as a repository of novel and thermostable cellulolytic and hemicellulolytic enzymes.

Keywords: Cellulase; Halophile; Rhodothermaceae; Rhodothermus; Xylanase.

Fig. 1

Circular genome map of Rhodothermaceae bacterium RA. From the outermost circle to the center: RNA genes (rRNA, tRNA, and ncRNA), Reverse CDS, Forward CDS, GC skew, and GC ratio

Fig. 2

Distribution and predicted numbers of GH in the genome Rhodothermaceae bacterium RA and other bacteria strains of the same genus. *indicates draft genome sequences