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Spirochaeta thermophila sp. nov., an Obligately Anaerobic, Polysaccharolytic, Extremely Thermophilic Bacterium

Helena Yu Aksenova¹, Frederick A. Rainey^2,,*, Peter H. Janssen², George A. Zavarzin¹ and Hugh W. Morgan²

¹Institute of Microbiology, USSR Academy of Sciences, Moscow, USSR
²Thermophile and Microbial Biochemistry and Biotechnology Unit, University of Waikato, Hamilton, New Zealand

^* Corresponding author.

ABSTRACT

Growth at temperatures of >60°C and utilization of polysaccharides have not been reported previously in members of the genus Spirochaeta. Two obligately anaerobic, extremely thermophilic (optimum temperature, 65°C) spirochetes were isolated from geographically distant thermal sites. These two isolates have chemoorganotrophic fermentative metabolism and grow on a variety of mono-, di-, and polysaccharides, including cellulose. The differences in pH and NaCl concentration optima between these organisms reflect the prevailing conditions at the sites from which they were isolated. DNA-DNA hybridization showed that the two strains exhibit a level of homology of 87%. On the basis of their morphological characteristics, their high level of homology with each other, and their extremely thermophilic and polysaccharolytic nature, we propose that these organisms should be included in the genus Spirochaeta as a new species, Spirochaeta thermophila; the type strain of this species is strain Z-1203 (= DSM 6578).