Iron uptake by Bifidobacterium thermophilum protoplasts

Area of Science:

• Microbiology
• Biochemistry
• Cell Biology

Background:

• Bifidobacterium thermophilum is a bacterium relevant to gut health.
• Iron uptake is essential for bacterial growth and function.
• Understanding iron binding mechanisms in bacteria is key to their metabolism.

Purpose of the Study:

• To investigate iron binding and internalization mechanisms in Bifidobacterium thermophilum.
• To differentiate between surface-bound and internalized iron in bacterial cells and protoplasts.
• To explore the role of cell surface and membrane components in iron interaction.

Main Methods:

• Preparation of Bifidobacterium thermophilum protoplasts using enzymatic digestion (lysozyme and protease).
• Ferrous iron uptake and binding studies on intact cells and protoplasts.
• Fractionation of protoplasts into soluble and particulate components for further analysis.
• Iron binding assays on membrane fragments.

Main Results:

• Protoplasts showed minimal iron internalization but significant surface binding, exceeding that of intact cells.
• Cells grown in iron-deficient media exhibited more extensive iron binding to protoplasts than iron-sufficient cells.
• Particulate fractions (membrane fragments) bound iron similarly to intact protoplasts, indicating outer surface binding.
• Iron-preloaded cells, when protoplasted, revealed iron bound to the inner membrane surface, dependent on cellular iron load.

Conclusions:

• Protoplast formation disrupts the iron transport mechanism of Bifidobacterium thermophilum while exposing surface iron-binding sites.
• The inner membrane surface of intact cells binds iron in a dose-dependent manner related to cellular iron uptake.
• Bacterial iron-binding sites, particularly on the inner membrane surface, may play a significant role in cellular iron metabolism.