Wetter is better: New microscopy methods improve accuracy of microbial biofilm imaging

Apr 26, 2011
Shewanella cells processed using cryogenic EM methods (left) and traditional techniques (right) have dramatic structural differences in their EPS morphology (arrows).

(PhysOrg.com) -- At a former uranium mill-tailing site in Rifle, Colorado, scientists are studying how microbes interact with minerals and metals to better understand processes that can help remediate the site. Electron microscopy, or EM, provides the resolution needed to study microbial transformation of metals, but there's a catch.

Typically, sample preparation for EM results in samples that are dehydrated, and dehydrating a microbial sample can shrink and distort its shape, or morphology. So scientists at Pacific Northwest National Laboratory and Lawrence Berkeley National Laboratory turned to state-of-the-art EM approaches at the Department of Energy's EMSL to get a "wetter," thus better, understanding of the morphology of metal biotransforming bacteria and their interactions with minerals.

The insights provided by this study are relevant to developing strategies for environmental remediation; in particular, to assess the impact of microbes on intermediate, or pore-scale, transport and biogeochemical processes. Studying these processes requires an understanding of hydrated microbial morphology, such as that of extracellular polymeric substances (EPS).

This video is not supported by your browser at this time.

EPS are a hydrated network of lipids, , and protein complexes commonly found associated with metals and radionuclides. They are also important in biofilm formation, and thus have implications for processes ranging from corrosion to diseases such as . EPS are typically among the most difficult biological structures to study in their native state, posing a major challenge for obtaining accurate EM images.

Using cultures of metal-reducing microorganisms and samples obtained from the U.S. Department of Energy's uranium-contaminated Integrated Field Research Challenge site in Rifle, Colorado, the scientists compared traditional sample preparation methods and techniques at EMSL, which is located at PNNL. Some of the imaging resources offered there range from high-resolution transmission electron microscopy and scanning to a suite of microscopy tools with cryogenic—or freezing—capabilities. EMSL is one of the few places in the U.S., and the only user facility, where such capabilities are currently available.

Their comparison showed that for lab-grown microbial cultures and natural biofilms, cryogenic EM methods yielded largely artifact-free images, with cells and extracellular matrix preserved in their close-to-natural hydrated state, whereas traditional methods caused substantial shrinkage of the highly hydrated—about 95 percent H2O—extracellular matrix. The ability to prepare and examine samples in the close-to-natural state is available to users through the EMSL user proposal process.

Explore further: Researchers successfully clone adult human stem cells

More information: Dohnalkova AC, et al. 2011. "Imaging hydrated microbial extracellular polymers: comparative analysis by electron microscopy." Applied Environmental Microbiology 77(4):1254-1262. DOI: 10.1128/AEM.02001-10.

add to favorites email to friend print save as pdf

Related Stories

Unique Uranium Source in Naturally Bioreduced Sediment

Nov 18, 2009

(PhysOrg.com) -- A recently published Pacific Northwest National Laboratory study of a naturally bioreduced sediment sample from a former uranium mill tailings site reveals insights that enhance understanding ...

The closest look ever at native human tissue

Dec 05, 2007

Seeing proteins in their natural environment and interactions inside cells has been a long-standing goal. Using an advanced microscopy technique called cryo-electron tomography, researchers from the European ...

Patience pays off with methanol for uranium bioremediation

Feb 23, 2009

The legacy of nuclear weapons and nuclear energy development has left ground water and sediment at dozens of sites across the United States and many more around the world contaminated with uranium. The uranium is transported ...

Long-distance communication, microbial style

Oct 06, 2010

Scientists knew that the microbe Shewanella oneidensis transformed the electronic structure of the iron oxide it touched in the ground as well as without direct contact. Scientists from Pacific Northwest National ...

Recommended for you

Researchers successfully clone adult human stem cells

16 hours ago

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Researchers develop new model of cellular movement

19 hours ago

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

For resetting circadian rhythms, neural cooperation is key

Apr 17, 2014

Fruit flies are pretty predictable when it comes to scheduling their days, with peaks of activity at dawn and dusk and rest times in between. Now, researchers reporting in the Cell Press journal Cell Reports on April 17th h ...

User comments : 0

More news stories

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Male monkey filmed caring for dying mate (w/ Video)

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Researchers develop new model of cellular movement

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Impact glass stores biodata for millions of years

(Phys.org) —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...