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| At a very early stage of our project we noticed that standardization in the phototrophic community needs to have an overhaul to allow for reproducible experiments. As we started doing growth curves we used to determine the light intensity via a planar quantum sensor that can only absorb photons from an angle of approximately 120° and only counts photons having a wavelength between 400nm-700nm. Because of the way we setup our incubator the illumination was coming from two different light sources, which needed to be measured individually. While our first attempts included measuring the intensity by facing the quantum sensor at the lights respectively and then converting these values by a factor accounting for spherical flux of light. We then came up with the idea to search for a scalar radiometer that has a detection surface of nearly 4π steradian, can only measures photosynthetic active radiation. With the help of this method we used to determine the exact amount of µmol photons/m<sup>2</sup> that can be used for photosynthesis. (400nm-700nm). | | At a very early stage of our project we noticed that standardization in the phototrophic community needs to have an overhaul to allow for reproducible experiments. As we started doing growth curves we used to determine the light intensity via a planar quantum sensor that can only absorb photons from an angle of approximately 120° and only counts photons having a wavelength between 400nm-700nm. Because of the way we setup our incubator the illumination was coming from two different light sources, which needed to be measured individually. While our first attempts included measuring the intensity by facing the quantum sensor at the lights respectively and then converting these values by a factor accounting for spherical flux of light. We then came up with the idea to search for a scalar radiometer that has a detection surface of nearly 4π steradian, can only measures photosynthetic active radiation. With the help of this method we used to determine the exact amount of µmol photons/m<sup>2</sup> that can be used for photosynthesis. (400nm-700nm). |
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| After we determined the light intensity via this method the doubling time of our strain drastically reduced. Doubling times from two hours we had before were now beaten and we achieved new lows of about 90 mins for the first time. | | After we determined the light intensity via this method the doubling time of our strain drastically reduced. Doubling times from two hours we had before were now beaten and we achieved new lows of about 90 mins for the first time. |
| We believe that the standardization of measuring light intensity has a huge impact in the field of phototrophic biology. What we often time stumbled upon when we were looking for literature on our iGEM project was that the information on light intensity in these papers were often inconsistent. Oftentimes the only values on the intensity were given in the unit µEinstein, but the needed details on how that number was measured, was missing. So some people would measure the intensities with a planar device, others would determine them via a spherical quantum sensor. | | We believe that the standardization of measuring light intensity has a huge impact in the field of phototrophic biology. What we often time stumbled upon when we were looking for literature on our iGEM project was that the information on light intensity in these papers were often inconsistent. Oftentimes the only values on the intensity were given in the unit µEinstein, but the needed details on how that number was measured, was missing. So some people would measure the intensities with a planar device, others would determine them via a spherical quantum sensor. |
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| During our skype call with James Golden he emphasized that a lot of experiments are simply not reproducible, because there is no way to tell how much light one has to expose their organisms to. Additionally, we got the feedback of Dr. Nicolas Schmelling that even professional cultivation devices from companies which are specialized on building them, can not deliver consistent and even illumination. | | During our skype call with James Golden he emphasized that a lot of experiments are simply not reproducible, because there is no way to tell how much light one has to expose their organisms to. Additionally, we got the feedback of Dr. Nicolas Schmelling that even professional cultivation devices from companies which are specialized on building them, can not deliver consistent and even illumination. |
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| To go even further, we think that the spectrum of the respective lamp should also be considered when talking about standardization. The light spectrum of our two lamps look as follows. | | To go even further, we think that the spectrum of the respective lamp should also be considered when talking about standardization. The light spectrum of our two lamps look as follows. |
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| Even though the standardization of the light quality seems to be a very hard task it should still be included in scientific works in order to give as much information as possible about the experimental setup. | | Even though the standardization of the light quality seems to be a very hard task it should still be included in scientific works in order to give as much information as possible about the experimental setup. |
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| We measured an equidistant grid of points at which we measured the average amount of photons (10 seconds) to minimize fluctuation. These data points were then interpolated with the help of a b spline surface to predict the amount of µmol photons at any given point of the incubator. This method is described in more detail on our <a href="https://2019.igem.org/Team:Marburg/Model">model</a> page. We believe that the standardization of measuring light intensity has a huge impact in the field of phototrophic biology and immensely helps to create reproducible experimental setups. | | We measured an equidistant grid of points at which we measured the average amount of photons (10 seconds) to minimize fluctuation. These data points were then interpolated with the help of a b spline surface to predict the amount of µmol photons at any given point of the incubator. This method is described in more detail on our <a href="https://2019.igem.org/Team:Marburg/Model">model</a> page. We believe that the standardization of measuring light intensity has a huge impact in the field of phototrophic biology and immensely helps to create reproducible experimental setups. |
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| We could show that light intensity had a big effect on reporter gene expression. | | We could show that light intensity had a big effect on reporter gene expression. |
| This displays the importance of standardization especially if one want to characterize parts such as promoters RBS terminator or engineer even more complex designs like genetic circuits or synthetic metabolic pathways. | | This displays the importance of standardization especially if one want to characterize parts such as promoters RBS terminator or engineer even more complex designs like genetic circuits or synthetic metabolic pathways. |