Team:XHD-Wuhan-A-China/Description
Project Inspiration and Description
Inspiration and Motivation
Soil is not only the substrate for human survival, but also the foundation for the growth of all things on earth. However, because of the industrialization process of the human world, the natural environment inevitably changes, especially the soil environment. The extensive unreasonable cultivation and abuse of chemical fertilizer cause soil hardening, the change of soil structure, the decrease of porosity, the increase of hardness and the decrease of infiltration capacity and even the degradation of soil fertility. Among them, the abuse of chemical fertilizer leads to obvious salinization and acidification of soil, which is one of the important reasons for soil hardening. We hope that our engineering bacteria can solve the soil problems caused by soil acidification and salinization and provide technical guarantee for the protection of soil environment and the safety of cultivated land.
Background
Soil acidification and salinization have become the main obstacles to the sustainable development of agriculture. The increase of soluble salt ion content in soil causes ion toxicity, which impair the absorption of nutrients by crops. In particular, the accumulation of nitrate often leads to soil acidification and inhibits the activities of soil nitrifying bacteria, which makes crops susceptible to nitrite poisoning. Soil acidification not only endangers the growth of crops, but also easily leads to the accumulation of nitrate in plants, reduces the quality of vegetables and even affects food safety. At present, the common methods to ameliorate soil secondary salinization are agricultural methods and water conservancy methods. But there are some problems such as it works slowly and waste of water resources.
Applying microbial agents is a good way to improve salinized soil, but there are many limitations in the use of microbial agents, such as the bacteria needs different requirements for growth environment and the efficiency of the transformation of nitrate into nitrogen of wild-type strains is not high. Rhizobia is a kind of bacteria that widely existing in soil roots, which can adapt to the growth of different soil materials. Moreover, many rhizobia have a certain denitrification ability, which can convert nitrate into nitrogen to a certain extent.
Our project
Considering different growth rates of rhizobium, Sinorhizobium Fredii HH103 was selected as the chassis organism in order to enhance the denitrification capacity of rhizobium. NapA and nirK genes are genes that exist in rhizobia and are closely related to the denitrification. In this project, the expression plasmid containing napA or nirK genes was introduced into rhizobia through synthetic biology technology, hoping to increase the copy number of napA or nirK genes in rhizobia and we want to enhance the denitrification of rhizobia in this way. Then, excessive nitrate in the soil can be better decomposed and the hardening effect caused by soil salinization can be alleviated.
References
Rady M M. Effect of 24- epibrassinolide on growth, yield, antioxidant system and cadmium content of bean (Phaseolusvnlgaris L.) plants under salinity and cadmium stress. Scientia Horticulturae,2011,129(2):232-237.
Ouni Y , Albacete A, Cantero E, et al. Influence of municipal solid waste (MSW) compost on hormonal status and biomass partitioning in two forage species growing under saline soil conditions. Ecological Engineering,2014,64:142-150.
Shi, W. , Zhang, C. , Zhi, Y. , & Zhou, P. . (2010). Transformation of nitrate nitrogen by three strains of bacteria isolated from facility culturing soils. IEEE. DOI: 10.1109/ICBBE.2010.5516777
