Team:Baltimore BioCrew/Proof Of Concept

2020 Baltimore Biocrew
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Proof Of Concept

Our project is based on the idea that iron is a limiting factor in the growth of cyanobacteria. In order to justify the basis for our project, we tracked the growth of cyanobacteria in various concentrations of iron. The result gave a better understanding of how iron affects its growth.

Also, our results demonstrated that our decision to engineer a Synechococcus strain with increased access to iron will likely increase the growth of the cyanobacteria, which provides proof of concept for the whole project .

In order to test the importance of iron to the phytoplankton population, Synechococcus CB0101 at an initial OD of 0.05 was put into five conical tubes containing SN growth media with different iron (ferric ammonium citrate) concentrations: No iron, 0.01X, 0.1X, 1X (0.023 mM), and 10X normal iron concentration. Stock concentrations were based on the UTex Culture Collection of Algae. Growth was measured by optical density (O.D.) after 2-3 weeks and by Secchi depth over 2 weeks.

From measuring the O.D. of the growth of Synechococcus CB0101 in varying concentrations of Fe(II) (Figure 1) it can be observed that as the concentration of Fe(II) increases in the media there is an increased growth of Synechococcus CB0101.

Measured Growth of Cyanobacteria Under Different Growing Conditions.
Figure 1: Optical density of Synechococcus CB0101 at varying concentrations of Fe(II). All values are normalized to no Fe(II) control. (A) O.D. for samples 1 and 2 were measured following 3 weeks of growth at 30°C. (B) O.D. for sample 3 was collected after 1 week of growth at 20°C.

In addition to direct O.D. measurements, we also measured Secchi depth over a period of time and converted these measurements into O.D (Figure 2). In this experiment, varied growth was also clear. The higher the iron concentration, the faster the sample grew.

Measured Growth of Cyanobacteria Under Different Growing Conditions.
Figure 2: Estimated optical density of Synechococcus CB0101 at varying concentrations of Fe(II). Secchi depth was collected for 2 weeks of growth at room temperature and converted to OD using a correlation curve. Initial (t=0 hours) OD of 0.05.