Washington, April 18 : Duke University researchers have moved a step closer to understanding how bacteria divide, something that may eventually lead to new antibiotics for curbing the multiplication of bacteria.
The researchers say that they have basically got fresh insights into the important role of a protein called FtsZ in the division process by deconstructing the process of bacterial division.
Bacteria generally divide by forming a ring called "Z ring" that pinches the cell in two. The ring has been so named after FtsZ, which forms a ring-shaped scaffold and then squeezes it smaller.
In bacteria, the Z ring also contains a dozen other proteins, all of which are believed to be essential for their division. It pulls in on the cell membrane by binding to another protein called FtsA, which has one end attached to the inner cell membrane and the other end connected to FtsZ.
When the Z ring constricts, it completely pulls in the membrane and nips the bacterium in two.
Dr. Masaki Osawa, lead researcher on the current study, cut FtsA out of the system by making an FtsZ that could bind directly to the membrane.
The researcher called the new system "membrane targeted FtsZ" (FtsZ-mts).
He first showed that the new protein assembled Z rings in bacteria, and then constructed a greatly simplified cell-division machine in microscopic oil droplets called liposomes, which demonstrated the important role of FtsZ in the division process.
The process enabled him to assemble Z rings in the completely artificial system, that is the liposome, a tiny hollow sphere of fat that mimics natural cell membranes.
For this research, the researchers mixed the liposomes with FtsZ and GTP, a molecule that provides energy.
They then observed the liposomes fusing and stretching into tubes that mimicked the shape of E. coli and other rod-shaped bacteria.
"It was a happy coincidence that the size and shape of the liposomes was similar to that of rod-shaped bacteria. These tubular liposomes are a new micro-structure, and their formation is still a mystery," says Harold Erickson, a professor of Cell Biology who jointly wrote the study report.
"We believe our simple system may recreate the mechanism that the earliest bacteria used to divide. They probably had FtsZ alone. Osawa's experiments show that FtsZ, a membrane tether, and the inside surface of a tubular membrane are all that's needed to assemble the Z ring and generate a constriction force," Erickson added.
Osawa said that the artificial Z rings were not sufficient to pinch the liposomes in half, "probably because their walls are much thicker than the membrane of a bacterium."
"We are now working to make thinner liposomes, so that we can achieve complete division," he added.
Erickson described FtsZ as the bacterial ancestor of the protein tubulin that makes the microtubules in animal cells, and is the target of a number of anti-cancer drugs like taxol.
He said that anything learned about the bacterial ancestor would help scientists understand microtubules, which help animal cells to keep their shape and control their movements.