Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Single-celled bacterium works 24-7

30.04.2008
Converting light to energy by day, moonlighting at night

Researchers at Washington University in St. Louis have gained the first detailed insight into the way circadian rhythms govern global gene expression in Cyanothece, a type of cyanobacterium (blue-green algae) known to cycle between photosynthesis during the day and nitrogen fixation at night.

In general, this study shows that during the day, Cyanothece increases expression of genes governing photosynthesis and sugar production, as expected. At night, however, Cyanothece ramps up the expression of genes governing a surprising number of vital processes, including energy metabolism, nitrogen fixation, respiration, the translation of messenger RNA (mRNA) to proteins and the folding of these proteins into proper configurations.

Cyanothece is a unicellular bacterium that can capture energy from light and also fix atmospheric nitrogen. As part of a daily diurnal cycle, Cyanothece stores the products of photosynthesis and nitrogen fixation so that they can be used at the proper time. This ability makes Cyanothece an ideal system to understand how a unicellular organism balances and regulates complex processes in the same cell.

The findings have implications for energy production and storage of clean, alternative biofuels.

The study was published in the April online issue of the Proceedings of the National Academy of Science. The research was funded by the U.S. Department of Energy in the context of a Biology Grand Challenge project administered by the Environmental Molecular Sciences Laboratory at the Pacific Northwest National Laboratory.

Bacterial biological clock

"One of the mysteries in cellular physiology is this business of rhythm," said Himadri Pakrasi, Ph.D., the George William and Irene Koechig Freiberg Professor in Arts & Sciences and lead investigator of this project. "Circadian rhythm controls many physiological processes in higher organisms, including plants and people. Cyanothece are of great interest because, even though one cell lives less than a day, dividing every 10 to 14 hours, together they have a biological clock telling them when to do what over a 24-hour period. In fact, cyanobacteria are the only bacteria known to have a circadian behavior."

Why does such a short-lived, single-celled organism care what time it is? The answer, according to this study, is that the day-night cycle has a tremendous impact on the cell's physiology, cycling on and off many vital metabolic processes, not just the obvious ones.

Among the obvious cycling processes are photosynthesis and nitrogen fixation. It is difficult for one cell to perform these two functions because the processes are at odds with one another. Fixing nitrogen requires nitrogenase, a catalyst that helps the chemical reaction move forward. Unhelpfully, the oxygen produced by photosynthesis degrades nitrogenase, making nitrogen fixation difficult or impossible in photosynthetic organisms.

Other filamentous cyanobacteria perform photosynthesis and nitrogen fixation in different, separate cells. As a single-celled bacterium, however, Cyanothece cannot separate these antagonistic processes in space. But it can separate them in time.

Agreeing with previous studies, this study found that Cyanothece genes for photosynthesis turn on during the day and genes for nitrogen fixation turn on at night. The surprise is the tremendous impact the day-night cycle has on the overall physiology of the cell.

"It goes far beyond just the aspects of nitrogen fixation and photosynthesis," said Pakrasi, who also directs Washington University's International Center for Advanced Renewable Energy and Sustainability (I-CARES) to encourage and coordinate university-wide and external collaborative research in the areas of renewable energy and sustainability — including biofuels, carbon dioxide mitigation and coal-related issues. The university will invest more than $55 million in the initiative.

Cyanothece's 'Dark Period'

To see the effect of day-night cycles on the overall physiology of Cyanothece, lead author Jana Stöckel, Ph.D., Washington University post-doctoral researcher, and other members of this research team examined the expression of 5,000 genes, measuring the amount of messenger RNA for each gene in alternating dark and light periods over 48 hours. At a given time, the mRNA levels indicated what the cells were doing. For example, when the researchers identified high levels of many mRNAs encoding various protein components of the nitrogenase enzyme, they knew that the cells were fixing nitrogen at that time, in this case, during the dark periods.

Of the 5,000 genes studied, nearly 30 percent cycled on and off with changing light and dark periods. These particular genes, the study found, also govern major metabolic processes. Therefore, the cycling of mRNA transcription, Pakrasi said, "provides deep insight into the physiological behavior of the organism — day and night."

During the day, Cyanothece busies itself with photosynthesis. Using energy from sunlight, carbon dioxide from the atmosphere, and water, Cyanothece produces glucose, a sugar it stores in glycogen granules, filling its chemical gas tank. At night, the Cyanothece ramps up production of nitrogenase to fix nitrogen, as expected. Since nitrogen fixation requires a lot of energy, Cyanothece uses the glycogen stored through a process called respiration. Because respiration requires oxygen, the cells conveniently use up this by-product of photosynthesis, likely helping to protect nitrogenase from degradation.

Through this cyclic expression of genes, Cyanothece is essentially a living battery, storing energy from the sun for later use. This feat continues to elude scientists searching for ways to harness sunlight and produce energy on a large scale. With this in mind, a new project for the Pakrasi team seeks to use the machinery of Cyanothece — its energy storage strategy, its anaerobic conditions that protect important enzymes — as a biofactory to produce hydrogen from sunlight, the ultimate clean energy source.

Gayle Geren | EurekAlert!
Further information:
http://www.wustl.edu

Further reports about: Cyanothece Expression Nitrogenase Pakrasi Protein bacterium fixation mRNA nitrogen organism photosynthesis

More articles from Life Sciences:

nachricht One step closer to reality
20.04.2018 | Max-Planck-Institut für Entwicklungsbiologie

nachricht The dark side of cichlid fish: from cannibal to caregiver
20.04.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>