Nav: Home

Ultrastructure of a condensed chromosome-like structure in a cyanobacterium

October 20, 2016

Researchers centered at Japan's National Institute for Physiological Sciences reveal details of the structure of compacted DNA transiently formed at the time of cell division in cyanobacteria.

Okazaki, Japan -

Eukaryotic cells, including human cells, form paired condensed chromosomes before cell division. The paired chromosomes are then equally divided into the daughter cells. Prokaryotic cells, including bacteria, do not have such a DNA distribution system.

Researchers working at the National Institute for Physiological Sciences (NIPS) and Saitama University have discovered that the photosynthetic cyanobacterium Synechococcus elongatus shows eukaryotic condensed chromosome-like DNA compaction prior to cell division and were able to reveal details of the transiently formed structure. The bacteria divide at the moment of transition from day to night if cultivated under rigorous 12-h light/12-h dark cycles. The ephemeral 3D structure of the compact DNA was captured by high-voltage cryo-electron tomography following rapid freezing. The researchers show that the structure is similar to the condensed chromosomes in eukaryotic cells. The compacted DNA also includes many small and paired polyphosphate bodies, some of which seem to maintain contact with DNA that appears to twist away from them, indicating that they may act as suppliers and regulators of phosphate for DNA synthesis. These new findings may deepen our understanding of how the eukaryotic cell arrived at a system using condensed chromosomes in the long evolution of biological cells.

For the study, published in Scientific Reports, the researchers used a combination of rigorous synchronized cultivation and sophisticated imaging by high-voltage cryo-electron tomography after rapid freezing to depict the transient 3D structure of the compacted DNA in cyanobacteria as thick as 1 μm. The polyphosphate bodies included in the compacted DNA may play a role as phosphate suppliers for DNA synthesis, which are duplicated alongside the DNA duplication.

"We know that the difference between prokaryotes and eukaryotes is in the DNA packaging and delivering system, where eukaryotes have developed a nuclear membrane to protect their genes and form condensed chromosomes to properly parcel the genome into the daughter cell, whereas prokaryotes do not have such a system" corresponding author Kazuyoshi Murata says. "Our new findings throw light on the duplication and segregation mechanisms of cyanobacterial DNA and point to an important role for polyphosphate bodies. They may give hints as to by what steps the evolution from prokaryote to eukaryote took place. "
The article "Ultrastructure of compacted DNA in cyanobacteria by high-voltage cryo-electron tomography" was published in Scientific Reports at .

National Institutes of Natural Sciences

Related Dna Articles:

Penn State DNA ladders: Inexpensive molecular rulers for DNA research
New license-free tools will allow researchers to estimate the size of DNA fragments for a fraction of the cost of currently available methods.
It is easier for a DNA knot...
How can long DNA filaments, which have convoluted and highly knotted structure, manage to pass through the tiny pores of biological systems?
How do metals interact with DNA?
Since a couple of decades, metal-containing drugs have been successfully used to fight against certain types of cancer.
Electrons use DNA like a wire for signaling DNA replication
A Caltech-led study has shown that the electrical wire-like behavior of DNA is involved in the molecule's replication.
Switched-on DNA
DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices.
More Dna News and Dna Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...