Draft 4/21

This was also about a talk I went to at Harvard. This talk was very dense on the engineering aspect of microbiology which I found interesting because it was something that I don’t typically think about. The main point of the talk was discovering ways in which we can categorize and catalog bacteria. The proposed method was by looking at bacterial cell envelopes and inducing a dipole on them to determine how they behave. The other half of the talk was about about how we can use electric fields to help introduce new DNA and genes to cells. This is where the talk became incredibly engineering heavy and a prototype machine that could carry out multiple electroporation experiments at once was introduced. The way that bacterial cells were categorized by their cell envelope was with a technique called low frequency dielectrophoresis. With this technique a dipole is induced on the cell by creating a non-uniform gradient. The bacterial cells were then placed in tubes that had a constriction point, it is at this point that the now polarized cells feel the dielectrophoresis force and clump at the constriction point. The bacteria used in this experiment was a mutant strain of Streptococcus mitis. A mutant was used because S. mitis typically has a virulence factor that causes clumping, the mutant had this virulence factor removed so that any clumping near the constriction point would be fully attributed to the dielectrophoresis force and not the virulence factor. Two other bacterial strains were used to observe polarizability. The first, Geobacter sulfurreducens polarizability was studied by observing its extracellular electron transfer mechanics. The second, Shewanella oneidensis polarizability was studied by looking at its Mtr pathway. This gene was later inserted into Escherichia coli to see if it was also impact the polarizability of it. The engineering part was to make a machine that carried out multiple electroporation experiments at once. This was done by condensing the apparatus down to the size of a pipette tip.