How Teichoic Acids Could Support a Periplasm in Gram-Positive Bacteria, and Let Cell Division Cheat Turgor Pressure.

Area of Science:

• Microbiology
• Biophysics
• Cell Biology

Background:

• Bacterial cytoplasm has higher osmolality than the growth medium, creating turgor pressure.
• The cell membrane (CM) cannot withstand high turgor; pressure transfers to the peptidoglycan cell wall (PGW).
• Gram-negative bacteria possess an isoosmotic periplasm, but this is unstudied in gram-positive bacteria.

Purpose of the Study:

• To investigate the potential role of a periplasmic space in gram-positive bacteria.
• To propose a mechanism for how teichoic acids could support an isoosmotic periplasm.
• To highlight the importance of an isoosmotic periplasm for cell division.

Main Methods:

• Semi-quantitative analysis of teichoic acid function in supporting periplasmic osmolality.
• Comparison of teichoic acid charge density to proteoglycans in articular cartilage.

Main Results:

• Teichoic acids' fixed anionic charge density (∼0.5 M) can attract Na+ ions, balancing cytoplasmic osmolality.
• This ionic balance can counteract a turgor pressure of approximately 19 atm.
• The calculated charge density is comparable to proteoglycans, suggesting similar pressure-supporting capabilities.

Conclusions:

• A periplasmic space is likely essential for periplasmic protein function, including peptidoglycan (PGW) remodeling by penicillin-binding proteins (PBPs).
• Teichoic acids are proposed as key molecules for maintaining an isoosmotic periplasm in gram-positive bacteria.
• An isoosmotic periplasm facilitates CM constriction and PGW synthesis during cell division by mitigating turgor pressure effects.