The Intersection of Biology and Nuclear Physics: How Detectors can Tease Apart Microbial Ecosystems*

Microorganisms live in complex and diverse ecosystems, making it difficult to separate individual species of microbes in environmental samples The scintillator layered imaging microscope for environmental research (SLIMER) presents a way to match metabolism to microbes by feeding radioactive substrate to a community and measuring their fluorescently dyed rRNA in a DNA microarray. Detecting the decays from a location in the array would allow you to see which individual species metabolized the substrate.   

SLIMER is composed of a microscope, scintillator, and electron multiplying-coupled camera device (EMCCD). Radioactive sources are set on a thallium-doped cesium iodide (CsI(Tl)) scintillator such that when ionizing radiation interacts with the scintillator, the photons released are directed into the microscope and to the EMCCD. The photons then excite electrons in the EMCCD and create secondary electrons, meaning that the original signal can be amplified greatly through these gains. 

This research attempts to create a calibration of energy for these decay processes through a Python program that can identify when a decay occurs and sum up the pixel intensities for the area of the decay. If done with multiple beta sources where their mean and endpoint energy in the continuum is defined, an estimation of what pixel intensities relate to what energy can be made. In the future, this would allow for identification of what decay energy is occurring in a sample.