Turgor Pressure and Possible Constriction Mechanisms in Bacterial Division.

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Bacterial cytokinesis begins with the assembly of FtsZ into a Z ring at the center of the cell. The Z-ring constriction in Gram-negative bacteria may occur in an environment where the periplasm and the cytoplasm are isoosmotic, but in Gram-positive bacteria the constriction may have to overcome a substantial turgor pressure. We address three potential sources of invagination force. (1) FtsZ itself may generate force by curved protofilaments bending the attached membrane. This is sufficient to constrict liposomes in vitro. However, this force is on the order of a few pN, and would not be enough to overcome turgor. (2) Cell wall (CW) synthesis may generate force by pushing the plasma membrane from the outside. However, this would probably require some kind of Brownian ratchet to separate the CW and membrane sufficiently to allow a glycan strand to slip in. The elastic element is not obvious. (3) Excess membrane production has the potential to contribute significantly to the invagination force. If the excess membrane is produced under the CW, it would force the membrane to bleb inward. We propose here that a combination of FtsZ pulling from the inside, and excess membrane pushing membrane inward may generate a substantial constriction force at the division site. This combined force generation mechanism may be sufficient to overcome turgor pressure. This would abolish the need for a Brownian ratchet for CW growth, and would permit CW to operate by reinforcing the constrictions generated by FtsZ and excess membrane.





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Osawa, Masaki, and Harold P Erickson (2018). Turgor Pressure and Possible Constriction Mechanisms in Bacterial Division. Frontiers in microbiology, 9(JAN). 10.3389/fmicb.2018.00111 Retrieved from https://hdl.handle.net/10161/16449.

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Harold Paul Erickson

James B. Duke Distinguished Professor Emeritus

Recent research has been on cytoskeleton (eukaryotes and bacteria); a skirmish to debunk the irisin story; a reinterpretation of proposed multivalent binders of the coronavirus spike protein. I have also published an ebook on "Principles of Protein-Protein Association" suitable for a course module or individual learning.

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