Project Development

For our project this year we wanted to capitalize on our resources at Purdue. In addition to our strong engineering programs we have top agriculture programs and extension efforts. The biggest problem facing the agriculture today is Food Security; how will we feed 9 billion people by 2050?

We tackled this issue by talking with professors in our College of Agriculture. In one conversation with Dr. Camberato, of the Ag Extension office, we discussed soil management strategies and how a university like Purdue tries to educate local farmers about innovations that they have systematically tested. Farmers nowadays are in great need and are willing to try anything for consistent and high yield crops, so much so that Dr. Camberato estimated each farmer probably spends up to 10,000 per acre on unproven strategies simply as result of rigorous sale strategies on the part of companies.

One day while discussing the history of Ag extension, Dr. Camberato showed Peter Mercado a black and white picture of a child playing in soil that was taken from China in Lake Michigan. Dr Camberato then stated that this family was able to increase the size and percent yield of their crop by supplementing their natural soil with the foreign soil taken from a ship. Curious as to what properties of the soil were able to accomplish this; we did more research and found that the likely culprit was probably microbes.

We decided to talk to Dr. Nakatsu, a microbial soil ecology expert, and realized the great diversity and ability of microbes to aid plant health. However given the enormous diversity and competition in naturally occurring soil, how would we go about managing the complexity? Could we benefit plants with just one microbe or a cocktail?

We dived into the literature on the rhizosphere and the use of nitrogen fixing bacteria as a safe and well known practice. We asked ourselves if there are microbes that could aid the uptake or bioavailability of nutrients in the soil. We realized that modern Ag practices focus heavily on the supplementation of nitrogen, phosphorus and potassium. But what about other nutrients like iron, calcium, sulfur and manganese?

We then came across an article by Scientific American titled, “Dirt Poor: Have Fruits and Vegetables Become Less Nutritious?” We found the article startling and looked into what deficiencies were most prominent in people and plants. We found that iron deficiency manifested in iron deficiency anemia was a huge problem. Now that we found our nutrient, how could we go about helping plants absorb more iron?

Plants uptake iron by 2 main mechanisms: non-grass plants reduction strategy; lowering the pH of the soil around them making Fe³⁺ to Fe²⁺, and the grass plant chelating strategy utilizing phytosiderophores or scavengers of Fe³⁺. We decided to exploit the biochemical pathway responsible for phytosiderophore production because bacteria naturally produce their own siderophores and plants can utilize them in iron-starved conditions. However another strategy we considered is using bacterial localization to roots circuits (used by imperial college auxin project 2011) and overexpression of membrane proton pumps on bacteria to decrease the pH of the soil and increase the bioavailability of Iron.

The question then became what microorganism would host our phytosiderophore producing circuit? We ultimately decided on Bacillus subtilis because it is a common soil microbe around the world and its sporulation stage allows for effective transport.