Team:Baltimore BioCrew/Description

2020 Baltimore Biocrew

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Project Description

Introduction

In 1/3 of the world’s oceans, the iron concentration limits phytoplankton growth. Iron is required for the photosynthesis and is a critical micronutrient for the base of the marine food web [5]. Phytoplankton populations have decreased by 1% annually [1], and this absence resonates up the food chain from tiny krill to massive whales [3]. Iron, in the form of magnetite, arrives at the ocean when wind blows it into the water. The concentration of iron dissolved in the ocean is very low because magnetite sinks to the seafloor and because microbes secrete molecules such as siderophores to capture most of the remaining iron [5].


Higher concentrations of iron in the ocean or a better ability to capture iron could stabilize phytoplankton. This would also reduce atmospheric carbon dioxide and preserve the Antarctic ice. Oceanographer John Martin first suggested adding iron to the ocean to stimulate phytoplankton growth more than 15 years ago and numerous trials have been conducted [2]; one discovered that each atom of iron could draw 10-100,000 atoms of carbon out of the atmosphere, a potential CO2 reduction of 15% [4].



Project Selection Process

In our early brainstorming process, we split into small groups and thought of five different problems we were interested in tackling. These ideas delved into different fields of science, such as creating a substance that could boost the immune system, a drug delivery compartment, using yeast for various purposes (as a biopesticide or food source), creating a probiotic using the MAFFs gene from Bacteroides thetaiotaomicron (a continuation of last year's project), and finally inserting iron-uptake genes into cyanobacteria in order for more efficient uptake in environments of limited iron concentration. Additional in-depth research into these ideas in small groups was conducted in order to create a presentation of a possible project to the entire team. There was much discussion about which ideas were both feasible and interesting. After multiple rounds of voting, we decided to pursue the iron-uptake in cyanobacteria idea. Consideration into applying for the Revive and Restore Grant competition also greatly impacted our decision in selecting our project, as the grant rewarded money to teams that were pursuing projects in environmental restoration. We felt that the iron-uptake in cyanobacteria project fit the objective for the grant the best.



Our Project

In choosing between the many different types of phytoplankton to work on, we chose one that consumes high levels of CO2, has a high replication rate, exists in the habitat of interest, and can cover substantial ocean surface area. We therefore chose to engineer Synechococcus sp. (cyanobacteria), a model organism that many iGEM teams have used before.

Our project will engineer cyanobacteria to transport iron into cells and reduce it to the bioavailable Fe(II) form. The increased iron levels will increase photosynthesis and growth of phytoplankton. This will stabilize the food supply for krill and the marine food chain and absorb CO2 from the atmosphere.

  • Our Aims arrow_downward
    1. We want to understand the effect of iron concentrations on cyanobacteria growth. We will characterize cyanobacteria growth by using modeling and experimental measurements.
    2. We want to modify Synechococcus sp. strain CB0101 to have the ability to grow in conditions with lower iron. This will be accomplished by adding iron transport, uptake, and binding genes from other cyanobacteria strains and species that evolved in iron poor environments.
    3. We want to use safe and ethical practices in modifying organisms. We will prevent phytoplankton blooms that are bad for the environment by engineering a safety mechanism, which will be regulated by an iron-sensitive promoter, so that our cyanobacteria die in environments where iron is not limiting. We will also improve upon existing iron-sensitive promoters by designing a promoter with stronger sensitivity so that cells die at lower iron levels.



  • References
    1. Boyce, D., Lewis, M. & Worm, B. Global phytoplankton decline over the past century. Nature 466, 591–596 (2010). https://doi.org/10.1038/nature09268
    2. Haiken, Melanie. "Can this carbon sink swim?" Mother Jones. March/April 2008. Vol. 33, Issue 2. (March 18, 2008
    3. Ryabov, A., de Roos, A., Meyer, B. et al. Competition-induced starvation drives large-scale population cycles in Antarctic krill. Nat Ecol Evol 1, 0177 (2017). https://doi.org/10.1038/s41559-017-0177
    4. Schiermeier, Q. Iron seeding creates fleeting carbon sink in Southern Ocean. Nature 428, 788 (2004). https://doi.org/10.1038/428788b
    5. Schoffman, H., Lis, H., Shaked, Y., & Keren, N. (2016, August 02). Iron–Nutrient Interactions within Phytoplankton. Retrieved from https://www.frontiersin.org/articles/10.3389/fpls.2016.01223/full