Anaerobic Growth of Hydrogenobacter thermophilus
Masaharu ISHII*a, Nare YUNa, Miho SUZUKIa, Tohru KODAMAb, and Yasuo IGARASHIa
a Department of Biotechnology, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, Japan
b Faculty of Textile Science and Technology, Shinshu University, 3-15-1, Tokida, Ueda-city, Nagano 386, Japan
Hydrogenobacter thermophilus TK-6 is a thermophilic hydrogen bacterium isolated from hot spring in Izu, Japan. In 1994, from the study of 16S rRNA sequence, the strain was shown to belong to one of the earliest branching orders of Bacteria. It is widely believed that the first living cell emerged in a hot environment where little or no oxygen existed. Since its isolation, strain TK-6 has been cultivated aerobically (oxygen partial pressure: around 15%). Taking the chemotaxonomic position of the strain into consideration, the strain was suspected to be a potential anaerobe.
For anaerobic growth, medium used for aerobic growth was supplemented with elemental sulfur (1 g/l). Aerobically grown cells of strain TK-6 were transferred to a glass jar-fermentor (volume: 2 1) which contained 1.51 of the medium. Gas mixture (H2:CO2 dioxide= 3:1, Total flow: 500 ml/min) was flown into the jar-fermentor and the growth was monitored by measurement of protein and H2S.
The strain turned up to have ability to grow anaerobically, which indicates the strain retains its original growth mode. This is the first case showing that Eubacterium with earliest branching order is able to grow anaerobically in a chemoautotrophic mode of growth.
