Thermoanaerobacter yonseiensis sp. nov., a novel extremely thermophilic, xylose-utilizing bacterium that grows at up to 85 °C

A novel strictly anaerobic, extremely thermophilic, spore-forming and xylose-utilizing bacterium, designated strain KB-1^TP (type and patent strain), was isolated from a geothermal hot stream at Sileri on Java island, Indonesia. The cells were rod-shaped, motile and had terminal spores. The newly isolated strain stained Gram-positive and the cells occurred singly or in pairs during the exponential growth phase. The temperature optimum for growth was 75 °C and growth occurred in the range 50-85 °C. The pH range for growth was 4.5-9.0, with an optimum at pH 6.5. Strain KB-1^TP grew chemo-organotrophically by fermenting a wide range of substrates such as glucose, fructose, d-xylose, lactose, maltose, sucrose, mannose, galactose, cellobiose, pullulan and soluble starch. Arabinose, xylan, cellulose, olive oil and Tween 80 were not fermented. The predominant fermentation end products after growth on glucose were lactate, acetate, ethanol, CO₂ and small amounts of isovaleric acid, butyric acid, propionic acid, 1-pentanol and 2-propanol. Thiosulfate was reduced to H₂S. Strain KB-1^TP was sensitive to tetracycline, chloramphenicol, penicillin G, neomycin, kanamycin, vancomycin and rifampicin at concentrations of 100 μg ml^-1. No effect was observed with chloramphenicol and neomycin at concentrations of 10 μg ml^-1. This indicates that strain KB-1^TP belongs to the bacterial domain. The G+C content of the DNA was 37 mol%. The comparison of the 16S rDNA sequence to that of closely related strains revealed that strain KB-1^TP belonged to clostridial cluster V, showing highest sequence identities (92.7%) to members of the genus Thermoanaerobacter. Taking into account the physiological and molecular properties of the new isolate, it is proposed that strain KB-1^TP should be classified as a new species of the genus Thermoanaerobacter, designated Thermoanaerobacter yonseiensis. The type strain, KB-1^TP, has been deposited in the Korean Federation of Culture Collections (KFCC 11116^P) as a patent strain and in the Deutsche Sammlung von Mikroorganismen und Zellkulturen as a type strain ( = DSM 13777^T).