A thermoacidophilic bacterium similar to Bacillus acidocaldarius

The thermoacidophilic strain TAC1 was isolated from a sulphatara field. It grows heterotrophically on a synthetic medium, containing yeast extract and carbohydrates at 50 to 70°C and pH 2 to 5. The cells are motile spore-forming rods utilizing, for instance, glucose, lactose, or sucrose as carbon substrate. They also used concentrated whey as nutrient medium. The maximum specific growth rate calculated from batch culture data of the strain TAC1 on glucose is 0.9 h−1 at 65°C and pH 3. The yield coefficient determined in a chemostat culture of the strain TAC1 on glucose, is 0.15 to 0.31 grams of cells produced per gram of glucose consumed (63 to 70°C, pH 2.2 to 4.0, dilution rate 0.2 to 0.4 h−1). The lipid fraction extracted from the cells consists of 72 to 93% of ω-cyclohexyl C17 and C19 fatty acids. The composition of lipid fraction varied with the pH value and the dilution rate but not with the temperature. In regard to the morphology and physiology of the isolated strain as well as the high percentage of ω-cyclohexyl fatty acids of the cell material, the strain TAC1 is similar to Bacillus acidocaldarius.