Characterization of two novel saccharolytic, anaerobic thermophiles, Thermoanaerobacterium polysaccharolyticum sp nov and Thermoanaerobacterium zeae sp nov., and emendation of the genus Thermoanaerobacterium

Two anaerobic, thermophilic, Gram-positive, non-spore forming bacteria with an array or polysaccharide-degrading enzymes were isolated from the leacha te of a waste pile from a canning factory in Hoopeston, East Central Illino is, USA. The results of 165 rDNA sequence homology indicated that their clo sest relatives belong to the saccharolytic, thermophilic and anaerobic gene ra of Thermoanaerobacterium and Thermoanaerobacter. Although, the evolution ary distances between these bacteria and their closest relatives are greate r than 11%, there is no defining phenotypic characteristic for the creation of a new genus. It is proposed that these bacteria should be placed in the genus Thermoanaerobacterium, which requires emendment of the genus descrip tion with regard to the reduction of thiosulfate to sulfur, because neither isolate is capable of this reduction. Thermoanaerobacterium polysaccharoly ticum reduces thiosulfate to sulfide, whereas Thermoanaerobacterium zeae is unable to reduce thiosulfate. The cells of both isolates are rod-shaped an d exist as single cells or sometimes in pairs. Cells are motile by means of flagella. Growth occurs between 45 and 72 degreesC, with optimum temperatu re of 65-68 degreesC at ph 6.8. The ph range for growth is from 4 to 8 at a temperature of 65 degreesC. Both organisms ferment glucose, arabinose, mal tose, mannose, rhamnose, sucrose, trehalose, xylose, cellobiose, raffinose, melibiose and melezitose. The major end products of fermentation with gluc ose are ethanol and CO,, with lesser amounts of acetate, formate, lactate a nd hydrogen. The DNA G+C contents of Thermoanaerobacterium polysaccharolyti cum sp, nov. and Thermoanaerobacterium zeae sp. nov. are 46 and 42 mol%, re spectively. The type strains are KMIHCJ(T)(= ATCC BAA-17(T) = DSM 13641(T)) and mel2(T)(= ATCC BAA-16(T) = DSM 13642(T)), respectively.