• Describe the role of FtsZ in cell division.
FtsZ is a protein that is involved in the cell division of MOST prokaryotes. It is
a protein that acts as a subunit and it assembles as a ring when the dividing
cell is expanding and its genetic material is copied. The ring is assembled
between the duplicated nucleoids – the nucleoids are on opposite poles and
they are basically identical.
Anchored to the inner surface of the CM, the FtsZ ring contracts by shedding
subunits into the cytoplasm; pulling the membrane inward eventually
pinching them off.
So basically FtsZ is assembled while/after the genetic material has been
copied and starts contracting when the nucleoids are in the emerging cells.
• Describe the different ways the synthesis of rigid cell wall polysaccharides
is coordinated with FtsZ ring
For organisms without a rigid cell wall, they just pinch off their membrane –
For organisms with a rigid cell wall, the situation is more variable for cell
division. The FtsZ ring not only pinches off the membranes but it serves also
as a scaffold for the synthesis of new cell wall material at the division site.
In some prokaryotes, the joint b/t the new cell wall material is degraded at
the same time the membrane is constricted by FtsZ. Then the cells just pinch
In the other prokaryotes, a cross wall (septum) is completed in the final
stages of FtsZ constriction. Later, enzymes digest part of the cross
• Explain the difference between FtsZ-based symmetric cell division,
asymmetric cell division, budding and bipolar cell division with respect FtsZ
ring localization, synthesis of new cell wall relative to the FtsZ ring and the
nature of the daughter cells relative to the parental cell.
Symmetric cell division is the most common in prokaryotes, exhibited by
cocci, rods, spirilla, etc. In a cell, there is a FtsZ ring in the middle with new
wall material synthesized on either side equally. The daughter cells are
identical. This means each cell is half new, half old. So symmetric cell
division = binary fission.
In non-spherical cells, symmetric cell division first involves the synthesis of
new cell wall material at other sites in addition to the division site. Another method is fragmentation done by Bdellovibrio. Fragmentation is
simply a variation on symmetric cell division but instead of 2 daughter cells
there are lots more. A long chain or filament of incompletely separated cells
is initially formed. The filament then undergoes FtsZ dependent cell division
resulting in simultaneous formation of unicells. Bdellovibrio reproduces in the
periplasm of other cells.
Incomplete cell division – In some prokaryotes, a significant fraction of cells
never completely separate after symmetric cell division. Therefore,
chains/filaments or clumps of cells result depending on the orientations of the
division planes. If they only divide on one plane you get a chain. If they
divide on 3 planes then you get a clump.
Asymmetric cell division – Caulobacter has a stalk that sticks to surfaces
(adhesive polysaccharide glue) and