Classification of ‘Anaerocellum thermophilum’ strain DSM 6725 as Caldicellulosiruptor bescii sp. nov.

Abstract

The thermophilic, cellulolytic, anaerobic bacterium 'Anaerocellum thermophilum' strain Z-1320 was isolated from a hot spring almost two decades ago and deposited in the German Collection of Microorganisms and Cell Cultures (DSMZ) as DSM 6725. The organism was classified as representing a new genus, 'Anaerocellum', primarily on its growth physiology, cell-wall type and morphology. The results of recent physiological studies and of phylogenetic and genome sequence analyses of strain DSM 6725 of 'A. thermophilum' obtained from the DSMZ showed that its properties differed from those originally described for strain Z-1320. In particular, when compared with strain Z-1320, strain DSM 6725 grew at higher temperatures and had an expanded range of growth substrates. Moreover, the 16S rRNA gene sequence of strain DSM 6725 fell within the Caldicellulosiruptor clade. It is therefore suggested that 'Anaerocellum thermophilum' should be classified as a member of the genus Caldicellulosiruptor, for which the name Caldicellulosiruptor bescii sp. nov. is proposed (type strain DSM 6725 T 5ATCC BAA-1888 T ). C. bescii sp. nov. DSM 6725 T is the most thermophilic cellulose-degrading organism known. The strain was able to grow up to 90 6C (pH 7.2) and degraded crystalline cellulose and xylan as well as untreated plant biomass, including potential bioenergy plants such as poplar and switchgrass.

Identification and characterization of a multidomain hyperthermophilic cellulase from an archaeal enrichment

“…The list includes the archaeon D. fermentans (up to 89 °C), and the bacterium C. bescii 6,19 . C. bescii was recently reported to grow at up to 90 °C on Avicel, filter paper and switchgrass 19 .…”

“…The list includes the archaeon D. fermentans (up to 89 °C), and the bacterium C. bescii 6,19 . C. bescii was recently reported to grow at up to 90 °C on Avicel, filter paper and switchgrass 19 . To increase the likelihood of discovering thermophilic cellulases, we targeted microbial consortia, rather than single isolates, that would grow around 100 °C on refractory crystalline forms of cellulose.…”

Biochemical and Mutational Analyses of a Multidomain Cellulase/Mannanase from Caldicellulosiruptor bescii

“…Recently, the complete genome sequencing of a thermophilic cellulose-and xylan-degrading bacterium (59), Caldicellulosiruptor bescii (previously classified as Anaerocellum thermophilum) (58), was accomplished (GenBank accession number CP001393) (12,30). The bacterium has been demonstrated to ferment crystalline cellulose, xylan, and insoluble extracts of the bioenergy feedstock switchgrass (12).…”

Complete Genome Sequences for the Anaerobic, Extremely Thermophilic Plant Biomass-Degrading Bacteria Caldicellulosiruptor hydrothermalis , Caldicellulosiruptor kristjanssonii , Caldicellulosiruptor kronotskyensis , Caldicellulosiruptor owensensis , and Caldicellulosiruptor lactoaceticus

“…The genus is globally distributed: species have been isolated from terrestrial geothermal hot springs in Russia (15,18,20), Iceland (3,16), Yellowstone National Park in the United States (9), and New Zealand (17) and, in one case, from solar-heated mud flats in Owens Lake, CA (11). With optimal growth temperatures ranging from 70 to 78°C, the genus Caldicellulosiruptor contains the most thermophilic microorganisms capable of biological cellulose hydrolysis known.…”