The growth, physiology and intermediary metabolism of bacillus stearothermophilus.

Sivasubramanian, Sundaram

Abstract

The aims of this work were to determine whether a functional tricarboxylic acid (TCA) cycle was present in vegetative cells of B. stearothermophilus, and to understand the effects of growth conditions on the carbohydrate metabolism and cytochrome content of the organism. In order to study the intermediary metabolism, the activities of key metabolic enzymes, the products of metabolism and the cytochrome content of the organism were determined under a variety of growth conditions. The dissolved oxygen tension was the most important environmental factor affecting the pathways of glucose utilisation. Aerobically, glucose was oxidised completely to carbon dioxide and the bacterium possessed a functional TCA cycle. Glycerol was a better substrate than glucose based on growth yield. The activity of the TCA cycle was lost even before the dissolved oxygen tension fell to zero and, anaerobically, glucose was fermented chiefly to lactic acid. Other products of fermentation were formic and acetic acids, and ethanol. B. stearothermophilus PS2 could not ferment glycerol. The pathways of carbohydrate utilisation during nitrate respiration depended on the nature of the carbon source. During growth on glycerol, the activities of all the TCA cycle enzymes including the 2-oxoglutarate dehydrogenase system were present. The activity of this enzyme complex could not be detected when the bacterium was grown on glucose. B. stearothermophilus PS2 growing at 55 °C could be thermoadapted to grow at 37 °C. The pathways of glucose utilisation were not affected by the change in temperature, though the growth yield obtained at 37 °C was double that obtained at 55 °C. At the lower temperature, an extra cytochrome species (cytochrome c545) was detected and this cytochrome was also detected in cells grown aerobically on limiting-glycerol at 55 °C, under which condition also the growth yield was high. B. stearothermophilus PS2 cells lost viability very rapidly when removed from a growdng culture. This loss of viability was dependent on the growth rate of the cells. Fast-growing cells lost viability more rapidly than slow-growing cells.

Citation

SIVASUBRAMANIAN, S. 1981. The growth, physiology and intermediary metabolism of bacillus stearothermophilus. Robert Gordon's Institute of Technology, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-1993306

• Thesis Type: Thesis
• Deposit Date: Jun 22, 2023
• Publicly Available Date: Jun 22, 2023
• DOI: https://doi.org/10.48526/rgu-wt-1993306
• Keywords: Geobaccilus stearothermophilus; Microbiology; Microorganisms
• Public URL: https://rgu-repository.worktribe.com/output/1993306
• Award Date: Nov 30, 1981