Featured Research

from universities, journals, and other organizations

New perspective for soil clean-up: Microscopic ciliates transport poisonous tar substances

Date:
March 24, 2014
Source:
Aarhus University
Summary:
Microscopic ciliates can increase the mobility of poisonous tar substances, PAHs, by up to 100-fold according to a new study. The results open new possibilities for cleaning soil that is contaminated with organic chemicals. PAH are toxic tar substances formed during incomplete combustion in, for example, car engines and cigarettes.

You must use a microscope to spot the new helpers that can assist in biological soil clean-up (bioremediation). They are small, mobile microorganisms, such as the unicellular slipper-shaped ciliates that can be found in stale water in a flower vase, where they feed on bacteria. New results from Aarhus University indicate that such mobile microorganisms can play a surprising key role in bioremediation of soil which is contaminated with so-called PAHs (Polycyclic Aromatic Hydrocarbons).

PAH are toxic tar substances formed during incomplete combustion in, for example, car engines and cigarettes. The classic PAH is benzo(a)pyrene, which was one of the first substances shown to be able to cause cancer. Until now PAHs were considered minimally mobile in soil because they bind to soil particles and only small amounts of PAH can be dissolved in water. However, the new study reveals that motile microorganisms can increase the mobility of PAHs significantly.

The experiments show that ciliates can enhance the transport of PAHs and potentially other hydrophobic chemicals up to 100-fold. This can be of great importance for the mobility and bioavailability of such substances and opens up new perspectives for cleaning PAH-contaminated soil because bioavailability is a crucial prerequisite for the biodegradation of PAHs.

First time ever

PhD student Dorothea Gilbert has been responsible for the tests with the ciliate Tetrahymena pyriformis. Together with Professor Philipp Mayer, who is presently employed at the Technical University of Denmark (DTU), she has developed a new test setup that allows exposing the ciliates to a concentration gradient while concurrently enabling their observation through a microscope in real time and measuring the transport of PAH by means of chromatographic methods.

"Until now, no one has ever It has to our knowledge not been shown before that microorganisms can actively move PAHs. Previously, we have seen that such substances can be transported passively with the water flow when they are bound to small particles, colloids or bacteria. Our experiments demonstrate that motile microorganisms such as Tetrahymena pyriformis swim actively with the PAHs, and it is important to notice that the ciliates can swim faster than PAHs can be transported by means of diffusion. This makes them very effective shuttles for PAHs on small spatial scale where there is no fluid flow.

Looking at several PAHs simultaneously, we observed that the mass transfer enhancement increased with the hydrophobicity of the PAHs. This is connected with the fact that more PAH is incorporated into the ciliates' lipid cell membrane, the more hydrophobic the PAHs" says Dorothea Gilbert.

New perspectives for soil bioremediation

These results question whether PAHs are quite as immobile in soil as has been thought until now.

"We expect that mobile microorganisms can transport PAHs in the stagnant water around and between soil particles and in water-filled pores. On such a micro-scale transport is generally based on diffusion, which for PAHs is very limited. Our study shows that mobile microorganisms can in such diffusion-limited condition increase the transport of PAHs. Our discovery can also be important with regard to bioremediation of PAH-contaminated soil.

The new findings indicate that microorganisms can increase the mobility of PAHs. By this means PAHs may become more accessible to bacteria which can degrade them, and make them more accessible to plant roots that can absorb them. Both are important prerequisites for biological treatment of PAH-contaminated soil," explains Dorothea Gilbert.

The findings have been published in the scientific journal Environmental Science & Technology.


Story Source:

The above story is based on materials provided by Aarhus University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Dorothea Gilbert, Hans H. Jakobsen, Anne Winding, Philipp Mayer. Co-Transport of Polycyclic Aromatic Hydrocarbons by Motile Microorganisms Leads to Enhanced Mass Transfer under Diffusive Conditions. Environmental Science & Technology, 2014; 140325154655002 DOI: 10.1021/es404793u

Cite This Page:

Aarhus University. "New perspective for soil clean-up: Microscopic ciliates transport poisonous tar substances." ScienceDaily. ScienceDaily, 24 March 2014. <www.sciencedaily.com/releases/2014/03/140324145359.htm>.
Aarhus University. (2014, March 24). New perspective for soil clean-up: Microscopic ciliates transport poisonous tar substances. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2014/03/140324145359.htm
Aarhus University. "New perspective for soil clean-up: Microscopic ciliates transport poisonous tar substances." ScienceDaily. www.sciencedaily.com/releases/2014/03/140324145359.htm (accessed July 22, 2014).

Share This




More Matter & Energy News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins