www.czu.cz ; www.raupp.info

Plants are a very potent tool used to remove toxic chemicals from
contaminated areas. In this process, called phytoremediation, transgenic
plants play an important role, January 2005 by Annette Ryser, Checkbiotech .

Many industrial, municipal and military areas have become contaminated
with hazardous pollutants. This constitutes a long lasting potential danger,
because emission is possible through air, ground, water or food chain.
Therefore, the grounds should be remediated, that is, cleansed from the
toxic substances. There are several methods to do this, and they are used
differently depending on the pollutant that needs to be removed.

One method is the microbiological remediation system (MRS), where
microorganisms are in charge of breaking down the pollutants. This approach
has proven to be quite successful. It can also be used in-situ, which means,
the contaminated ground can be cleansed without being removed. That is an
important factor in cases of broad contamination, because removing the
contaminated soil would be too expensive. The MRS can only remove harmful
substances that are organic, but it removes them very effectively. This is
in contrast to most of the physical and chemical remediation methods, which
usually leave by-products.

Besides the MRS method, another option is to use plants. There are, for
example, many plants that are known to naturally remove heavy metals. This
process is called phytoremediation, and it promises to be an inexpensive and
resourceful method. It is also very suitable for continuous remediation and
large areas, since plants grow over a long time without needing much more
than water.

Many reports for phytoremediation use transgenic plants. By genetically
enhancing plants, the cleansing power of fungi, bacteria or in some cases
plants can be given to plants that, in the end, more efficiently remove the
toxic substance. Since many microorganisms are potent bioremediators, fungal
and bacterial enzymes from microorganisms are often used to enhance the
cleansing power of plants. An example for this are plants that reduce
organic mercury with a bacterial mercury reductase, and are therefore more
resistant to toxic levels of mercury (1).

Dr. Y. Iimura?s laboratory, at the National Institute of Advanced Industrial
Science and technology (AIST) in Tsukuba Ibaraki, Japan, recently found that
genetically engineered tobacco (Nicotiana tabacum) could degrade organic
pollutants in the ground such as bisphenol A (BPA), pentachlorophenol (PCP)
and other chlorophenols (2). What Dr. Iimura?s laboratory did was, they took
a gene from a known, detoxifying, fungal enzyme (Coriolus versicolor) called
laccase III, and inserted it into tobacco plants.

During their studies, Dr. Iimura?s laboratory learned that the transgenic
tobacco not only produced the new enzyme, but also released it into the
surrounding soil ? a process that is called exudation. When their modified
tobacco plants were put to the test, Dr. Iimura?s laboratory found that the
plants were able to purify the soil of BPA and PCP after one week. Moreover,
they showed in a different experiment that transgenic plants with the
ability to remove BPA effectively also removed PCP from aqueous solution.

In-situ remediation of grounds through plants will hopefully soon become an
easy and very useful tool. Dr. Y. Iimura hopes that the results from his
laboratory will translate into plant-based technologies that will allow for
quicker and more efficient removal of pollutants from contaminated soil.

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