Quorum Sensing Lab Report

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Recently there has been a rising interest in studying social microbial behavior, which can provide fundamental information about the development of severe infections in host organisms by pathogenic bacteria. These microorganisms demonstrate highly social behaviors such as the ability to communicate by producing, releasing, detecting and responding to small signaling molecules. This process, named quorum sensing (QS), allows a bacterial population to regulate its population’s behavior in response to the effective density of neighboring microbial species. However, only a few studies have explored this complex process in low-cell-number/high-density populations. Such studies are of great medical significance since numerous infectious diseases …show more content…
Using this approach, we will confine P. aeruginosa bacteria tagged with mCherry, a fluorescent-protein-based reported, within 3D microstructures on the optical fiber tip. We will then expose the bacterial structure with an excitation source to create excited states promoting fluorescence, which we will detect using a photomultiplier tube (PMT). The fluorescence is an expression of mCherry, which gets activated when cells respond to several environmental factors like QS signals or oxygen levels that promote changes in gene expression. For instance, if bacteria are participating in QS, then the genes controlled by QS will be expressed, consequently turning fluorescence on. Thus, we will use the activation of mCherry’s expression as an indicator of the interactions between the bacteria within microstructures and the environment of interest. The optical fiber sensor is designed and currently being built in our laboratory. Briefly, a green HeNe laser is used as the excitation source to match the excitation wavelength of mCherry. The optical fiber does not only transmit excitation light to the tip of the fiber but also to collects the emitted light. A dichroic filter is placed before the detector, to selectively filter fluorescent light. We have designed a photon counting system controlled by a LabView program, which converts the detector’s signal to a number of counts over

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