Team:XHD-Wuhan-China/Description
Project Inspiration and Description
Inspiration
Exploration of Mars has never been stopped because Mars seems the only possible plan B for human habitation within the solar system. And 2020 is the unusual year of Mars exploration, many countries have launched Mars rovers to conduct exploration missions to Mars. One of the important tasks is to explore the possibility of humans migrating to Mars, and whether humans can be self-sufficient on Mars with only a small amount of supplies. On Mars, agricultural crops are the main source of food, so the normal growth of plants is crucial. We hope that the soils on Mars could be used for crop production. Our project is a trial to promote the dissolution of mineral phosphate in Martian soil and make it suitable for farming.
Background
The content of phosphorus in plants is second only to nitrogen and potassium, which is very important for the growth and development of plants. Phosphorus is one of the components of many important compounds in plants, and it's involved in many important physiological and biochemical processes of plants, such as photosynthesis, respiration, energy storage and transmission, and cell division. During the growth and development of crops, reasonable supplementation of phosphate fertilizer can promote the growth of early roots of plants, improve crop resistance and stress resistance, promote crop maturity and improve crop quality. Mars contains a large amount of phosphate, the total amount is about 5-10 times the total amount of phosphate on Earth. But the phosphorus on Mars mainly exists in the form of dolomite (Ca9NaMg(PO4)7) and chloroapatite (Ca5(PO4)3Cl), which are insoluble phosphates. When the pH value is close to 7, The phosphorus release amount of chloroapatite is 0.0226 ± 0.0009 mmol/L, which is much smaller than the concentration of phosphate fertilizer application (the concentration of foliar phosphate fertilizer is about 19.6 ~ 83.8 mmol/L). To meet the needs of crops' growth, it is necessary to release the phosphorus element from insoluble phosphates.
Phosphate-dissolving microorganisms are a type of microorganisms that can convert poorly soluble phosphate in the soil into soluble phosphate. it mainly secretes small molecular organic acids (involving Pyrroloquinoline quinone(PQQ) and Glucose dehydrogenase(GDH)) to decrease the pH of the soil, thereby promoting the dissolution of phosphate. In 2003, Nivedita et al. transformed the PQQ synthesis gene in Deinococcus radiodurans(DR) into E. coli, completing the function of glucose dehydrogenase, realizing the conversion of glucose to gluconic acid, decreasing the pH value of the solution, and promoting the dissolution of insoluble phosphate. However, neither phosphorus-dissolving microorganisms nor Escherichia coli can cope with the harsh environment on Mars. DR has special bacterial structure, super DNA repair ability, efficient antioxidant defense system and cell purification system, can survive the harsh environment of Mars.
Our Project
In response to strong radiation on Mars, we consider using DR as biological chassis to construct genetic circuit related to phosphate dissolution, so that it can dissolve insoluble phosphate in the harsh environment of Mars. Besides DR can synthesis PQQ by its own. Therefore, we just need to transform the glucose dehydrogenase (gcd) gene into DR. It then can synthesize GDH enzyme which along with PQQ can catalyze the production of gluconic acid, decrease the pH and solubilize phosphate. In addition, in order to improve the efficiency of dissolution, we also transformed the synthesized gabY gene into DR to enhance the binding efficiency of GDH and PQQ and increase the activity of GDH. Our team hopes to provide new solutions to transform the Martian soil and explore the possibility of growing crops on Mars.
References
Ahemad, Munees. Phosphate-solubilizing bacteria-assisted phytoremediation of metalliferous soils: a review[J]. Biotech, 2015, 5(2):111-121.
Adcock C T , Hausrath E M , Forster P M . Readily available phosphate from minerals in early aqueous environments on Mars[J]. Nature Geoence, 2013, 6(10):824-827.
Babu-Khan S , Yeo T C , Martin W L , et al. Cloning of a mineral phosphate-solubilizing gene from Pseudomonas cepacia.[J]. Applied & Environmental Microbiology, 1995, 61(3):972-978.
Khairnar N P , Misra H S , Apte S K . Pyrroloquinoline-quinone synthesized in Escherichia coli by pyrroloquinoline-quinone synthase of Deinococcus radiodurans plays a role beyond mineral phosphate solubilization.[J]. Biochemical & Biophysical Research Communications, 2003, 312(2):303-308.
Simpson R R J . Soil Microorganisms Mediating Phosphorus Availability[J]. Plant Physiology, 2011, 156(3):989-996.
Xiao-Fei C , Meng N , Fei F , et al. Research Progress on the Radiation-resistant Mechanisms of Deinococcus radiodurans[J]. Biotechnology Bulletin, 2017.
