Staphylococcus aureus but not Staphylococcus epidermidis can acquire iron from transferrin

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Iron Metabolism

Background:

• Staphylococci cause infections in iron-restricted environments within the host.
• Efficient iron acquisition is crucial for bacterial survival and virulence.

Purpose of the Study:

• To investigate the ability of Staphylococcus aureus and Staphylococcus epidermidis to acquire iron bound to human transferrin.
• To compare iron uptake mechanisms between these two staphylococcal species.

Main Methods:

• Transferrin was labeled with radioactive iron (55Fe).
• Uptake assays were performed on Staphylococcus aureus and Staphylococcus epidermidis grown under iron-restricted and iron-plentiful conditions.
• Siderophore, reductase, and protease activities were assessed.

Main Results:

• Staphylococcus aureus NCTC 8532 demonstrated iron uptake from transferrin during mid- to late-exponential growth.
• This iron acquisition by Staphylococcus aureus was iron-regulated and did not require direct cell-transferrin contact.
• Siderophore production was detected in Staphylococcus aureus, but not reductase or protease activity.
• Staphylococcus epidermidis ATCC 14990 could not acquire iron from transferrin and did not produce siderophore, reductase, or protease.

Conclusions:

• Staphylococcus aureus possesses a mechanism to extract iron from transferrin, contributing to its ability to thrive in vivo.
• The inability of Staphylococcus epidermidis to utilize transferrin-bound iron may correlate with its lower virulence compared to Staphylococcus aureus.
• Differences in iron acquisition strategies are key factors in staphylococcal pathogenesis.