Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Uranium 'pearls' before slime

09.08.2006
PNNL-led team discovers that bacteria roll out carpet of goo that converts deadly heavy metal into less threatening nano-spheres

Since the discovery a little more than a decade ago of bacteria that chemically modify and neutralize toxic metals without apparent harm to themselves, scientists have wondered how on earth these microbes do it.

For Shewanella oneidensis, a microbe that modifies uranium chemistry, the pieces are coming together, and they resemble pearls that measure precisely 5 nanometers across enmeshed in a carpet of slime secreted by the bacteria.

The pearl is uranium dioxide, or uraninite, which moves much less freely in soil than its soluble counterpart, a groundwater-contamination threat at nuclear waste sites.

The U.S. Department of Energy estimates that uranium contaminates more than 2,500 billion liters of groundwater nationwide; over the past decade, the agency has support research into the ability of naturally-occurring microbes that can halt the uranium's underground migration to prevent it from reaching streams used by plants, animals and people.

Assembling a battery of evidence, scientists have for the first time placed the bacterial enzymes responsible for converting uranium to uraninite at the scene of the slime, or "extracellular polymeric substance" (EPS), according to a study led by the DOE's Pacific Northwest National Laboratory in today's advance online edition of PLoS Biology.

"Shewanella really puts a lot of stuff outside the cell," said PNNL chief scientist Jim Fredrickson, the study's senior author. "It's very tactile compared with pathogens, which go into hiding to evade detection by the immune system."

Another oddity is Shewanella's ability to "breathe," or reduce, metals the way we human beings do oxygen. When oxygen is unavailable, Shewanella can pass excess energy during respiration in the form of electrons to metal and alter the metal's chemistry in the bargain--for instance, turning soluble uranium into solid, insoluble uraninite (uranium dioxide).

Fredrickson, PNNL staff scientist/lead author Matthew Marshall and colleagues wondered whether uranium-reducing components in that stuff outside the cell, the EPS, might help Shewanella seek out and lock up heavy metals.

To pose that question, which remains open, they first had to prove that the same metal-reducing enzymes--proteins called c-type cytochromes--associated with uraninite formation in the outer membrane could also be found outside the cell in the EPS.

This they did through a variety of experiments that included creating mutant strains unable to make outer-membrane cytochrome, or OMC, leading to an excess of uraninite particles forming only inside the cell, in the periplasm – the region between the microbe's cell and outer membrane. In nonmutants, on the other hand, OMC and uraninite were found mainly outside the cell in association with the EPS.

Collaborators from Argonne National Laboratory applied X-ray fluorescence microscopy at the Advanced Photon Source to show that iron, which is also found in OMC, was in the uraninite-EPS complex. Combining high-resolution microscopy and OMC-specific antibodies, the researchers repeatedly found the metal-reducing proteins in the uraninite-EPS complexes.

The authors noted that the OMC-containing EPS may be involved in the transfer of electrons outside the cell or is possibly a way the microbes shed the uraninite particles.

"Regardless," Fredrickson said, "the sticky EPS may behave like glue and bind the uranium particles to soil, further impeding its migration in the environment."

Bill Cannon | EurekAlert!
Further information:
http://www.pnl.gov

More articles from Life Sciences:

nachricht Newly discovered bacteria-binding protein in the intestine
08.12.2016 | University of Gothenburg

nachricht The balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

Decoding cement's shape promises greener concrete

08.12.2016 | Materials Sciences

Will Earth still exist 5 billion years from now?

08.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>