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Title: Osmoregulation in Staphylococcus aureus
Author: Pourkomailian, B.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1995
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Osmoregulation in Staphylococcus aureus has been studied. Glycine betaine was found to act as an osmoprotectant by stimulating specific growth rate and salt tolerance of osmotically stressed S. aureus cells. The accumulation of this compatible solute was accomplished via two constitutive Na+ dependant transport systems, a high-affinity system (Km = 3μM; Vmax = 26nmol. min-1 mg total protein-1) and a low-affinity system (Km = 133μM; Vmax = 155 nmol. min-1 mg total protein-1). The high-affinity system is specific for glycine betaine and its activity is not greatly stimulated by osmotic pressure. The low-affinity sytem transports proline and proline analogues and its activity is stimulated by increases in external osmolarity. Proline transport is achieved via two similar systems. Through transposon mutagenesis it was demonstrated that the low-affinity glycine betaine transport system and the low-affinity proline transport system are the same system. The low-affinity system is the major system responsible for the accumulation of glycine betaine. This is the more important system for the osmoregulation strategy of S. aureus. All three transport systems have been demonstrated to be subject to feedback regulation. The internal compatible solute concentration dictates the level of activity of the transport systems. A mutant has been isolated that lacks the low-affinity system and the high-affinity proline transport system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available