Scientists deconstruct process of bacterial division

Apr 17, 2008

Duke University researchers have made a major advance in understanding how bacteria divide. This could lead to new antibiotic treatments that prevent dangerous bacteria from multiplying.

Normally, bacteria divide by forming a ring that pinches the cell in two. The ring is called a “Z ring” after the protein FtsZ, which forms a ring-shaped scaffold and then squeezes it smaller. In bacteria, the Z ring also contains a dozen other proteins, all believed to be essential for division.

The Z ring normally pulls in on the cell membrane by binding to another protein, 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.

But cell biology research scientist Masaki Osawa, Ph.D., cut FtsA out of the system by making an FtsZ that could bind directly to the membrane, and called it "membrane targeted FtsZ" or FtsZ-mts.

First, Osawa demonstrated that the new protein, FtsZ-mts, assembled Z rings in bacteria.

Then he constructed a greatly simplified cell-division machine in microscopic oil droplets, called liposomes, that demonstrated the important role of FtsZ in the division process. He was able to assemble Z rings in this completely artificial system, the liposome, a tiny hollow sphere of fat that mimics natural cell membranes.

To do this, Osawa mixed the liposomes with FtsZ and GTP, a molecule that provides energy. On a microscope slide the liposomes fused and stretched 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,” says co-author Harold Erickson, professor of cell biology. “These tubular liposomes are a new micro-structure, and their formation is still a mystery.”

During the experiment, fluorescently labeled FtsZ-mts was initially on the outside of the liposomes, but some of the tubular liposomes ended up with FtsZ on the inside. “We don’t know how this happens, but it is a key to the discovery,” Osawa said.

Inside the liposome the FtsZ formed multiple closed rings that aligned perpendicular to the length of the tube, just as Z rings form in bacteria. They also slid back and forth, and where they collided, they stayed together and formed brighter Z rings. And as the Z rings grew in brightness, they visibly pulled the wall of the liposome inward.

“The Z rings are clearly generating force and causing the constriction,” Osawa said. A movie the team made shows several constrictions in the wall occurring at the sites of the bright Z rings. When the GTP in the liposome is used up, the tube eases out of its constrictions into its original shape.

“We believe our simple system may recreate the mechanism that the earliest bacteria used to divide. They probably had FtsZ alone,” Erickson said. “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.”

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,” Osawa noted. “We are now working to make thinner liposomes, so that we can achieve complete division.”

Erickson said that FtsZ is the bacterial ancestor of tubulin, the protein that makes the microtubules in animal cells and is the target of a number of anti-cancer drugs like taxol. Although FtsZ is not sensitive to taxol, anything learned about the bacterial ancestor will help us understand microtubules, which help animal cells to keep their shape and control their movements, he explained.

Source: Duke University

Explore further: Anaerobic co-digestion of farm-based manure, food waste, are there benefits vs. landfilling?

Related Stories

FAA's Airworthiness Directive issued to avoid power loss

21 hours ago

A fix for a software problem that could possibly result in power loss in Boeing 787s has been ordered. Federal Aviation Administration officials adopted a new airworthiness directive (AD), effective as of ...

More than 2,200 confirmed dead in Nepal earthquake

Apr 26, 2015

A powerful aftershock shook Nepal on Sunday, making buildings sway and sending panicked Kathmandu residents running into the streets a day after a massive earthquake left more than 2,200 people dead.

Recommended for you

Just like humans, dolphins have social networks

1 hour ago

They may not be on Facebook or Twitter, but dolphins do, in fact, form highly complex and dynamic networks of friends, according to a recent study by scientists at Harbor Branch Oceanographic Institute (HBOI) ...

Norway plans to slash subsidies to fur farms

1 hour ago

Norwegian fur farmers denounced Tuesday a government proposal to slash financial support to the controversial industry and warned that it could lead to farm closures in vulnerable rural areas.

Hitting the borders of expansion

5 hours ago

Why does a species not adapt to an ever-wider range of conditions, gradually expanding its geographical range? In their paper published on May 5 in PNAS (Proceedings of the National Academy of Sciences), Jitka Polecho ...

Fire linked to dieback spread

6 hours ago

Fire has the potential to increase the range and severity of Phytophthora dieback in native plant communities infected with the disease, suggests a study at the Stirling Range National Park near Albany.

How mixing light with salt makes a smolt?

6 hours ago

For decades, researchers have tried to find out what regulates changes in salmon when they transform from being freshwater to saltwater fish. Now they have come a little closer to an answer.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.