Team:NAU-CHINA/Proof Of Concept
PROOF OF CONCEPT
Proof of Concept
Proof of Concept
Considering that our project’s aim is to recover extra harmful selenates and transform them into useful and valuable SeNPs, it is of great significance for us to conduct corresponding experiments to preliminarily demonstrate that our project can truly work in a realistic environment.
So we managed to get in touch with the environmental chemistry laboratory of our school’s Resources and Environmental Science Institute. With their help, we collected waste water sample from secondary sedimentation tank of waste water treatment plant. In this case, we were able to incubate our engineered bacteria in an approximate waste water environment.
Acquisition of the desired SeNPs in this experiment can preliminarily prove that it is workable to recover selenium element in waste water. It laid a solid foundation for the future development of our project.
Fig.1&2 The processing of Se-rich waste water
Fig.3 SeNPs fermented solution from Se-rich waste water with 1/4 hoagland
SeNPs has been proved to have corresponding biological values in microorganism, plant and medical science. For example, SeNPs with the polysaccharide could inhibit tumor proliferation and migration of zebrafish embryos and have the effects of anti-angiogenesis; Cs-SeNPs could also modulate the photosynthesis parameters, antioxidant enzymes activities and essential oils in Dracocephalum moldavica L. under cadmium toxicity stress; furthermore, SeNPs suppressed Triticum aestivum L. crown and root rot diseases induced by Fusarium species and improve yield under drought and heat stress; low concentrations of SeNPs have also been reported to increase wheat and tomato yields, and increase the activities of related antioxidant enzymes.
When we acquired the SeNPs from experiments mentioned above, it is necessary to demonstrate our final product can actually meet our stakeholder’s interest, whom, in this scenario, are mainly farmers. That is why we conducted the following alfalfa promoting experiments to verify our idea.
Due to school facilities and laboratory limitations, we preliminarily selected and verified the bacteriostatic activity and biological effect of promoting plant growth of SeNPs produced by our project. However, due to iGEM safety policy and special properties of Magnaporthe, it was difficult to conduct experiments on the inhibition of Magnaporthe by SeNPs because Magnaporthe is pathogenic and may cause some unexpected harm. So, in order to verify the biological effects of SeNPs we produced, we chose to treat alfalfa seedlings with different concentrations of SeNPs, since we don't have enough time to cultivate plants such as wheat and rice.
Fig.4 SeNPs had influence on alfalfa seedling growth. To prove this characteristic, we designed a plant experiment. The plant used in the experiment was alfalfa (M. sativa L. cv. Biaogan) produced by the Clover Group. Four-day-old alfalfa seedlings were incubated in different concentrations of SeNPs. Afterwards, phenotypic photos were taken (A), bar: 1cm.The fresh weight and dry weight of root and shoot per 30 seedlings were analyzed (B, C). Within each set of the experiments, bars with different letters are significant different at P < 0.05 according to Duncan’s multiple range test.
As shown in Fig.4, compared to the control samples, SeNPs concentration of 0.5g/L significantly increased the fresh weight and dry weight of plants' roots and shoots, and it grew the best of the four samples (Fig.4A). However, the inhibitory effect was observed in two other SeNPs treatments with high concentrations, which showed lower dry weight and fresh weight as compared with the control samples. The same result has been reported in previous reports. It's a pity that we conducted this experiment after we finished constructing the response surface model and acquired the most stable SeNPs, so we didn't have enough time to detect some of the changes inside the plants, like changes in antioxidant enzyme activities. And our experiment only proved that the SeNPs we produced has biological activity and can promote plant growth, the biological effects of SeNPs on plants still need further exploration. To sum up, the results demonstrated that our project can be implemented in agricultural field, such as promoting plant growth in the form of SeNPs fertilizer.