Effect of Iron-Uptake System on the Growth of Staphylococcus aureus according to the Iron Concentration and Oxygen Tension

Lee, Seung Il; Shin, Sung Heui

Abstract

BACKGROUND: We previously reported that activity of iron-uptake systems (IUS) influenced on the growth of Staphylococcus aureus in body fluids which are relatively iron-restrictive conditions. Iron and oxygen are closely related each other in several microbial metabolism. In the present study, we tried to investigate the effect of IUS on the growth of S. aureus according to the iron concentration and oxygen tension. METHODS: SR-1 strain, whose IUS are defective, was isolated from the standard strain, ATCC 6538. These two strains were cultured under the aerobic, microaerobic and anaerobic condition in the iron-sufficient BHI and iron-depleted BHI, respectively. Bacterial growth was measured by optical density. RESULTS: Growth of both strains was inhibited in the iron-depleted BHI. Growth of parental strain was more active in the iron-sufficient BHI as well as in the ion-depleted BHI than that of SR-1 strain. Growth of both strains was more active under the aerobic condition than under the microaerobic or anaerobic condition. In the iron-depleted BHI, parental strain showed a striking difference of growth according to the oxygen tension. In the iron-depleted BHI, growth of SR-1 strain was markedly inhibited regardless of oxygen tension. CONCLUSION: IUS influenced more on the growth of S. aureus in the iron-depleted environments than in the iron-sufficient environments, and under the aerobic condition than under the microaerobic or anaerobic condition in the iron-depleted environments. These results indicated the possibility that oxygen as well as iron regulate activity and expression of IUS.