The United Nations estimates global population has increased by 1 billion over 12 years and will near 9.8 billion by 2050 [4]. This increase has meant social demand has also grown at an unparalleled rate. However, a more pressing issues is that of food security. Food security is defined as one’s ability to have adequate access to sufficient food. Said food must be safe and nutritious as for an individual to maintain a healthy and active lifestyle.

To match demand, the agricultural sector oft utilises synthetic fertilisers to improve crop growth. Nitrogen, phosphate and potassium (NPK) based fertilisers are used as they provide crops with essential macronutrients required for growth. NPK consumption is predicted to increase to 201.7 million tonnes by the end of 2020 [5].

Synthetic NPK fertilisers significant increases and yield of popular crops such as maize and soybean (3) but they also play a large role in in climate change. Nitrogenous fertilisers are produced by the Haber-Bosch process. This process is highly energy intensive, requiring 600kg of natural gas to produce 1000kg of ammonium, producing 670 million tonnes of CO2 per annum [6].

Repeatedly, studies show fertiliser application has a negative long-term impact on soil health. Synthetic fertilisers cause soil pH to decrease which degrades soil crumbs. This results in compact soil with reduced water drainage and air circulation; both of which have negative impacts on plant-root health [7].

This is not the only local impact of synthetic fertilisers. Accumulation of plant nutrients in bodies of water, resulting from surface run-off, leads to eutrophication. Eutrophication, from Greek meaning ‘well-nourished’, impacts water quality and allows algal blooming [8]. Algal blooming can impact biodiversity through toxin production and promotion of a hypoxic environment[9]

Eutrophication may have a larger humanitarian impact in the future. Eutrophication causes an increase in grey water percentage; the polluted water associated with industry. If grey water is not processed, then clean drinking water availability is reduced. This will likely impact rural areas of less economically developed countries where money and infrastructure is not readily available to cover water processing costs.

Residents are forced to either drink unsafe water or travel further to access water that is safer, however, these oases may become even rarer as water sources become exhausted or contaminated. This issue becomes more concerning when considering that 48% of the total population of Africa relies upon agriculture [10], a continent that experienced a 10.6% increase in total fertiliser demand between 2012 and 2018 [11].

These issues are expected to become more widespread in the future, with the aforementioned population increase and current demands for agriculture produce putting more pressure on farmers to maintain, if not increase, usage of synthetic fertilisers. As such, to overcome risks moving into the future, research into more sustainable nitrogen fertilisers and their substitutes should be pursued.

An effective solution would overcome both the energy expenditure and pollution associated with inorganic fertilisers but without losing properties such as broad and simple usage. Therefore our solution aims to create a single-application, broad host range sustainable alternative in the form of an engineered root endophyte that acts as a microbial adapter. This endophyte is Pseudomonas sp..

A Gram-negative bacterium with a diverse metabolism, Pseudomonas sp. has been highlighted as a diverse plant growth promoting bacterium [12] capable of colonising a broad range of plant roots [13].

Pseudomonas sp. is known as a natural plant growth promoter for numerous reasons;

• It produces a siderophore that liberates iron [14], consequentially liberating phosphorus too.[15]
• It has anti-fungal properties (protecting from pathogens).[16]
• It is nematophagous and produces nematode/protozoa repellents, protecting from parasites. [17]
• Produces anti-insectal toxins, protecting from pests. [18]
• Induces systemic resistance and tolerance.[19]

With all these features, Pseudomonas sp. is already an ideal organism for improving crop yields, but the Newcastle iGEM project takes this a step further.

By engineering Pseudomonas sp. to express novel genes the team aims to manipulate the soil microbial community via chemical attraction/repulsion to achieve desired processes. In our case this is a nutrient sustaining soil but there are no limits! From soil remediation to pest control, this project aims to create a chassis out of Pseudomonas sp. so future scientists can manipulate the soil community in any way they like.

Our prototype focuses on sustaining the amount of Nitrogen present in soils without adding fertiliser or causing run-off. To combat this, we have introduced flavonoid biosynthesis genes to Pseudomonas sp. that attract free-living/non-nodulating nitrogen fixing bacteria to improve the nitrogen content of the soil [20].

This method means that one application is all that is needed to improve the nutrient availability for a plants life-time. This combined with the other protective roles of Pseudomonas sp. acts to improve crop yields without genetically modifying plants and without Nitrogen/Phosphorus fertilisers. Even if we only reduce fertiliser use by a tiny amount, globally this would make a huge difference in terms of energy usage and pollution.