Biochemical Properties of A Thermophilic Alkalophile

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A thermophilic alkalophile (IC strain) which can grow well in an alkaline medium at over 55°C was isolated from soil samples, and identified as Bacillus licheniformis; its growth on a neutral medium was, however, very poor. This strain was able to grow at 37°C as well as at 55°C, but the specific growth rate at 55°C was about twice as high as that at 37°C under alkaline conditions.
The intracellular pH remained below 9.5 when Na⁺ was present in the medium. Na⁺ stimulated the alanine uptake by cells or membrane vesicles, but was not required ATP synthesis.
Intracellular enzymes were stable on heat treatment up to 60°C. The residual activity of enolase after heating at 60°C for 10min was about 80%. Cytochrome oxidase in membrane vesicles was completely stable up to 58°C for 30min. These enzymes were also resistant to SDS treatment, more than 50% of their activities remaining at 5% SDS.