Caldicellulosiruptor kristjanssonii sp. nov., a cellulolytic, extremely thermophilic, anaerobic bacterium

Abstract

A cellulolytic anaerobic bacterium, strain 177RlBT, was isolated from a biomat sample of an Icelandic, slightly alkaline, hot spring (78 "C). Strain 177R1BT was rod-shaped, non-spore-forming, non-motile and stained Gram-negative at all stages of growth. It grew at 45-82 "C, with an optimum growth temperature around 78 "C. A t 70 "C, growth occurred at pH 58-8-0, with an optimum near pH 7.0. At the optimum temperature and pH, with 2 g cellobiose I-' as substrate, strain 177R1BT had a generation time of 2 h. During growth on Avicel, strain 177R1BT produced acetate, hydrogen and carbon dioxide as major fermentation products together with small amounts of lactic acid and ethanol. INTRODUCTIONAnaerobic micro-organisms from extreme environments and, in particular, their fermentation products and thermostable enzymes, have been the subject of much research over the past 15-20 years. Much interest has been centred on the cellulose-and hemicellulosedegrading bacteria, as these polymers constitute a large renewable resource in nature. Many of the validly described anaerobic, thermophilic, cellulose-degrading bacteria form spores and are placed in the genus Clostridium (Wiegel, 1992). In contrast, a number of anaerobic, cellulolytic, extremely thermophilic, non-spore-forming bacteria have been isolated (Huang et al., 1998;Hudson et al., 1990; t Present address: MATFORSK, Norwegian Food Research Institute, Osloveien 1, N-1430 As, Norway.The EMBL accession number for the 165 rRNA gene sequence of strain l77R1 BT is NO0481 1. Rainey et al., 1993a; Sissons et al., 1987;Svetlichnii & Svetlichnaya, 1988; Svetlichnii et al., 1990; Taya et al., 1985; Wiegel, 1992). The cellulolytic strains have been mostly isolated from neutral to alkaline hot springs. Two strains were isolated from compost (Rainey et al., 1993a) and Caldicellulosiruptor owensensis was isolated from sediment taken from Owens Lake, California, USA (Huang et al., 1998). Common features of the isolates are their high temperature habitat, ability to ferment polysaccharides, high optimum growth temperature (68-75 "C), a maximum growth temperature lower than 85 OC, a pH range for growth between pH 4.0 and 9-0, and their apparent lack of ability to form spores. By comparative 16s rDNA sequence studies, Rainey and co-workers, and later Huang and co-workers, have shown that these organisms cluster together in one group (Huang et al., 1998; Rainey et al., 1993a, b;Rainey & Stackebrandt, 1993). MladenovskaIn the present study, we have characterized a new METHODSAll diagnostic tests were performed at least twice, with triplicate determinations. Mean values are reported.Growth medium. The anaerobic medium used for cultivation was as previously described (Angelidaki et al., 1990), with the following adjustments. Avicel (2 g IF1 ; microcrystalline cellulose, FMC International) was used as carbon and energy source. The medium was supplemented with 0.10 g yeast extract 1-1 and no cysteine was added. The medium was adjusted to pH 7.0 and autoclaved at 140 "C for 20 min. Befor...

Caldicellulosiruptor Core and Pangenomes Reveal Determinants for Noncellulosomal Thermophilic Deconstruction of Plant Biomass

“…This finding seems reasonable, given that all isolated species have been described as having the ability to grow on cellobiose (12,27,31,61,69,80,98). Since these bacteria are assumed to live in plant biomass-degrading communities, even if a species is lacking strong cellulolytic machinery it would be beneficial to maintain the ability to import cellulose hydrolysis products.…”

“…Since plant biomass deconstruction could be accelerated at elevated temperatures, thermophilic microorganisms have been considered catalysts for CBP (8). Of particular note in this regard are members of the extremely thermophilic genus Caldicellulosiruptor that inhabit globally diverse, terrestrial hot springs (12,27,56,57,61,69,80,98) and thermally heated mud flats (31). Caldicellulosiruptor species are Gram-positive bacteria and typically associate with plant debris; consequently, all isolates characterized to date hydrolyze certain complex carbohydrates characteristic of plant cell walls (8, 97).…”

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.…”

Caldicellulosiruptor kronotskyensis sp. nov. and Caldicellulosiruptor hydrothermalis sp. nov., two extremely thermophilic, cellulolytic, anaerobic bacteria from Kamchatka thermal springs

“…The group of thermophilic cellulolytic prokaryotes includes two aerobic species, Rhodothermus marinus and Acidothermus cellulolyticus, and numerous anaerobes of the genera Caldicellulosiruptor, Clostridium, Spirochaeta, Fervidobacterium and Thermotoga (reviewed by Bergquist et al, 1999). At the time of writing, the genus Caldicellulosiruptor comprised five species with validly published names: Caldicellulosiruptor saccharolyticus (Rainey et al, 1994), Caldicellulosiruptor lactoaceticus (Mladenovska et al, 1995), Caldicellulosiruptor owensensis (Huang et al, 1998), Caldicellulosiruptor kristjanssonii (Bredholt et al, 1999) and Caldicellulosiruptor acetigenus (Onyenwoke et al, 2006). All members of the genus Caldicellulosiruptor are extremely thermophilic, cellulolytic, non-spore-forming anaerobes with Gram-positive type cell wall, and are capable of fermenting a wide spectrum of carbohydrates.…”

“…Temperature range for growth is 45-82 uC, with optimum growth at 70 uC; pH range for growth is 6.0-8.0, with optimum growth at pH 7.0. Rainey et al, 1994); 2, Caldicellulosiruptor lactoaceticus (Mladenovska et al, 1995); 3, Caldicellulosiruptor owensensis (Huang et al, 1998); 4, Caldicellulosiruptor kristjanssonii (Bredholt et al, 1999); 5, Caldicellulosiruptor acetigenus (Onyenwoke et al, 2006); 6, strain 2002 T (Caldicellulosiruptor kronotskyensis sp. nov.); 7, strain 108 T (Caldicellulosiruptor hydrothermalis sp.…”