Contaminant Transport In The Fungal PipelineJuly 25, 2012
Leipzig, Germany - Fungi are found throughout the soil with giant
braiding of fine threads. However, these networks have surprising
functions. Only a few years ago researchers from the Helmholtz
Centre for Environmental Research (UFZ) discovered that bacteria
travel over the fungal threads through the labyrinth of soil pores,
much the same as on a highway. Now, together with British colleagues
from the University of Lancaster, the UFZ researchers have come upon
another phenomenon. Accordingly, the fungal networks also transports
contaminants which are otherwise largely immobile in the ground.
These living pipelines can therefore contribute to the restoration
of impacted areas, write the researchers in the journal
Environmental Science & Technology. But what if the fungal network offers good travel possibilities not only for bacteria, but for contaminants as well? Nevertheless, it is known that the transport of nutrients which the fungus requires to survive takes place within the hyphae. Why should this not function, then, with other substances? Together with colleagues from the University of Lancaster, the UFZ researchers have now pursued this question. For their investigations the researchers employed a pseudo-fungus with the name Pythium ultimum, which is widespread in the soil. This was placed on a central plate with nutrients, proceeding from which it could extend its hyphae to the right and left to two further sources of nourishment. The three nourishment stations were connected by rectangles of nourishment-free material. However, there were several gaps between the nourishment plates and rectangles containing only air. These were intended to simulate the air-filled pores in the ground. At the edge of a rectangle the UFZ researchers applied a polycyclic aromatic carbohydrate with the name Phenanthrene. They then investigated at regular intervals whether this substance could be detected in other areas of the test path. "The results were astounding", says Lukas Y. Wick. Within a few hours the carbohydrate had migrated from one end of the experimental arrangement to the other – from ten to one hundred times faster than it could have by simple diffusion. Furthermore, it overcame the air gaps with no difficulty, which was not possible over the same path without hyphal networks. "The hyphal networks are therefore not only highways for bacteria, but also pipelines for contaminants", concludes Lukas Wick. "Per hour a single hypha can transport up to 600 times the weight of an individual bacterium". With a special microscope of the British colleagues it was even possible to observe this transport in detail. Accordingly, the contaminant migrates through the cell wall into the interior of the hyphae. There it is enclosed in tiny bubbles, which Pythium ultimum then actively pumps through its far-reaching network. Contaminants in motion In this way the fungal pipeline mobilises not only Phenanthrene, but also other substances virtually insoluble in water and therefore sooner immobile substances. The researchers repeated the experiment with a number of different PAHs, and all were found to be efficiently transported. However, over longer paths the transport of small molecules functioned better than that of large molecules. "Presumably the latter are not taken up as well by the hyphae", in the opinion of Lukas Y. Wick. In this experiment even the longer paths consisted of only a few centimetres. This may appear to be relatively little, however it could still prove decisive for better contact between the contaminants and their decomposers, as the fungal pipeline effortlessly overcomes the minute air barriers between the water-filled soil pores. The researchers hope that this effect can be utilised in future for the restoration of impacted ground. The targeted use of fungal networks could accelerate the degradation of PAHs and perhaps also of other substances virtually insoluble in water. "But this may function only when one combines the right fungi and bacteria", explains Lukas Y. Wick. Some types of these organisms are simply not compatible or even mutually inhibit each other. Consequently, the UFZ researchers are now searching for the most suitable partners for their microbial contaminant eliminator team. Kerstin Viering SOURCE: Helmholtz Association of German Research Centres Copyright © 1996 - 2012, VertMarkets, Inc. All rights reserved. To subscribe or visit go to: http://www.wateronline.com |