The Physiological Response of Staphylococcus Aureus Mf-31 to Conditions of Reduced Water Activity
Anderson, Carl Byron
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https://hdl.handle.net/2142/70071
Description
Title
The Physiological Response of Staphylococcus Aureus Mf-31 to Conditions of Reduced Water Activity
Author(s)
Anderson, Carl Byron
Issue Date
1983
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Abstract
The mechanism by which Staphylococcus aureus was able to grow in environments at reduced water activity (a(,w)) was investigated. This project was approached by studying the influence of reduced a(,w) on the intracellular free amino acid pools, amino acid transport, glutamine synthesis, and proline oxidation in S. aureus. In addition, the effect of a(,w) on the intracellular free amino acid pools of eight other bacterial species was examined. Further, the water binding capacity of 22 L-amino acids from a(,w) 0.33 to 0.95 was determined.
Amino acid analysis of the intracellular amino acid pool of S. aureus revealed that the principle amino acids were aspartic acid, glutamic acid, and alanine when grown at a(,w) 0.99. When challenged with NaCl (a(,w) 0.97), the principle amino acids were proline, glutamine, and alanine. The accumulation of glutamine had not been reported before and was the result of its synthesis.
Amino acid analysis of a salt sensitive mutant of S. aureus showed that proline was not accumulated in response to a reduced a(,w). Later studies showed that proline accumulation was the result of transport and was required for S. aureus to grow in environments with a(,w) less than 0.96. Kinetics of proline transport in S. aureus revealed the existence of at least two permeases in addition to a permease that functions during conditions of reduced a(,w). Analysis of the influence of reduced a(,w) on the activity of proline oxidase and glutamine synthetase showed that enzyme activity was dependent more upon the cation concentration than on ionic strength or a(,w).
Amino acid analysis of eight other bacterial species revealed that no single observable event could account for the regulation of osmotolerance in these bacteria. In general, an increase in the total amino acid pool and the accumulation of a specific amino acid was found to occur. The water binding capacity of 22 free amino acids revealed that all but proline and (gamma)-aminobutyric acid were poor water binders over the a(,w) range 0.33 to 0.95. Water binding capacity was enhanced by the presence of monovalent cations. Bacteria also accumulate potassium in response to a reduced a(,w). Thus, the interaction of cations and amino acids may be a general mechanism used by bacteria to maintain a state of hydration within the cell when challenged with an environment at reduced a(,w).
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