What it´s all about

Figure 1: Plants can internalize pollutants dissolved in water [The Guardian, 2011]

Today science and technology are eager to protect the environment from further harm and reverse the damage already done. Of these technologies, bioremediation and phytoremediation in particular are very promising ones as they try to help nature help itself. Bioremediation is defined as "the process of judiciously exploiting biological processes to minimize an unwanted environmental impact; usually it is the removal of a contaminant form the biosphere." [Prince, 2000] Phytoremediation is the concept of removing pollutans either directly by plants themselves or by specialized bacteria living in a symbiosis with plants. There is a multitude of different pollutants that are primary targets for remediation such as Polychlorinated biphenyls (PCBs), insecticides such as dichlorodiphenyltrichloroethane (DDT), heavy metals such as cadmium or mercury or pharmaceutical products such as macrolide antibiotics, diclofenac or ethinylestradiol.

Phytoremediation vs. Bioremediation

Table 1: Costs of different techniques for soil remediation.
Type of treatment Range of costs, $/ton
Phytoremediation 10-35
In situ bioremediation 50-150
Soil venting 20-220
Indirect thermal treatment 120-300
Soil washing 80-200
Solidification/stabilization 240-340
Solvent extraction 360-460
Incineration 200-1500

So why did we choose Phytoremediation over the approach of classical Bioremediation using bacteria like so many iGEM-teams do?

First of all, because the overall applicability of plants is much higher than that of bacteria. Provided with a sufficient safety mechanism, transgenic plants can be deployed almost everywhere and only need water and light to sustain themselves. In comparison, bacteria are much harder and to contain and generate more maintenance costs. And secondly, thanks to all the fantastic work of other iGEM-teams in previous years, we had the possibility to choose from a wide variety of existing BioDegradation bricks!

Our aim was to use the excellent existing bricks and build upon the work of previous teams while improving their applicability by establishing a completely new chassis.

Standing on the Shoulders of Giants

As we established our idea we investigated several remediation projects done by previous teams to look for ways to improve them or even come up with a totally new approach. Looking through interesting projects like those of Bielefeld 2012, Imperial College London 2010 and of course the algae project of Bilkent UNAM Turkey, we noticed that there have only been a few phytoremediation projects in the iGEM competition. We thought there could be a more suitable chassis for remediation and stumbled upon the well established model organism Physcomitrella patens. As nobody in our team had ever worked with moss (or with plants for that matter) we had a lot of research to do. As there was nobody working with this organism at our whole university we had to look for other universities to find some experts we could win as an advisor for our team. Thankfully Prof. Reski´s homepage provided the necessary papers, methods and details and he was also willing to support our project. Having looked into it, we were conviced that this plant is what we have been looking for and that it would be great to introduce it to the iGEM community.

Table 2: Previous remediation projects
Team Year Organism Description
Peking University 2010 E.coli Heavy metal decontamination of aquatic environments via binding proteins
UT Dallas 2010 E.coli Establishing E.coli as a biosensor for environmental pollutants using fluorescence
METU Turkey 2010 E.coli Designing a biosensor to detect CO as a dangerous pollutant
USeoul Korea 2010 E.coli Using fluorescence proteins to detect various heavy metals in water
TU Delft 2010 E.coli Enabling hydrocarbon degradation in aqueous environments
Michigan 2009 E.coli Sensing and degrading toluol
UQ Australia 2009 E.coli Uptake and reduction of mercury in water
Cornell University 2009 B.subtilis Creating a cadmium sensor

Seeing all those great projects we decided not only to improve biodegredation by looking at the actual degredation processes but more importantly by establishing a wholly new chassis to the iGEM competition and to phytoremediation in general.

Why Physco, why?

So why exactly did we choose Physcomitrella patens as the basis for our remediation project? One big point was that we wanted to make our filter system available for everyone and bacteria just didn´t do the trick for us: Harder to control and harder to grow and implement in nature. We wanted something that could be deployed in a few simple steps and would be self-sustainable and self-renewing. Short, we wanted an autotrophic organism which could be easily established in an aquatic environment. Not only does our moss provide us with these features as it only needs water, light and carbon dioxide to grow and can be grown on soil as well as in water but it can also be easily cultivated in bioreactors which gives us the possibility to envision industrial scale waste-water treatment based on our system. For more information on Physcomitrella patens you can read through the Physcomitrella patens wiki page.

Constructed Wetlands as a large-scale application of Phytoremediation

In the last decades Phytoremediation made the transition from a solely scientific approach to an industrial scale water treatment technique. Today large amounts of water are treated through constructed wetlands as it poses one of the simplest and most cost-effective ways to treat sewage-waters either on their own or in symbiosis with a traditional treatment plant.

How do they work and why do we need them?

Figure 2: Constructed wetland diagram. [EPA open water system]

Natural wetlands, as well as constructed ones, are systems in which plants and microorganisms form complex biotopes capable of filtering, degrading or inactivating various substances in the water. The wetland, slowing the speed of the passing water, can trap suspended solids in the vegetation which also accumulates pollutants by absorbing them. As these wetlands are a perfect habitat for microorganisms various degredation processes take place ridding the water from a variety of pollutants.

Figure 3: Constructed wetland plant [EPA]

Higher environmental standards in first world countries as well as the growing industrialization have led to a skyrocketing demand in sewage water treatment. The capacities of traditional treatment systems have shown to be ineffective and too expensive. Constructed wetlands pose a real alternative to conventional technologies as they are not only reliable and cost-effective but the most natural and environmental friendly way of cleaning water. They leave no waste behind, are self-sustaining and have no demand for artificial energy. As opposed to most other environmental measurements, constructed wetlands are very attractive for businesses as they are cheap alternatives to existing systems rather than costly additions.


[Prince, 2000] Prince, R. C. (2000). Bioremediation. Kirk-Othmer Encyclopedia of Chemical Technology.

[The Guardian, 01.11.2011] "Plants working to combat pollution. Examining phytoremediation - using plants to mitigate pollution"

[] Professor Reski´s Homepage

[United States Environmental Protection Agency Homepage]

G.Kvesitadze: Biochemical Mechanisms of Detoxification in Higher Plants, Springer-Verlag, Heidelberg 2006

[EPA,2001] Brownfields technology primer: selecting and using phytoremediation for site cleanup, pp 1-24