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  • Thumbnail for Investigation of the type VI secretion system of Acinetobacter baylyi in relation to growth rate, DNA release, and long term stationary phase
    Investigation of the type VI secretion system of Acinetobacter baylyi in relation to growth rate, DNA release, and long term stationary phase by Slay, Erin Jennifer

    Acinetobacter baylyi is a gram-negative soil dwelling bacterium. The strain ADP1 is highly competent which allows for easy manipulation of its genes. The genes of interest here are a set of the genes encoding a type VI secretion system (T6SS), namely tssG, tssF, tssE, tssB, and tssC. This T6SS is homologous to the bacteriophage tail. The tail of the bacteriophage is used to inject DNA into a bacterial cell. Therefore, we hypothesized that the T6SS could be used to release DNA into the environment. Over the course of this research, we investigated ADP1 bacterial cells that contained knockouts of the various parts of the T6SS. The knockouts were used to determine which, if any, of the parts of the T6SS play a role in DNA release. We also tested the mutants for differences in growth rate and survival in long-term stationary phase (LTSP). LTSP is a phase in which 99% of the cells die off and the remaining 1% begin to eat waste and dead cells to survive. We examined survival in LTSP because another T6SS gene, vgrG (ACIAD0167), is known to be expressed during LTSP (Lostroh and Voyles, 2010). The gene is also necessary for survival during LTSP (Stanley and Lostroh, 2010) and twitching motility (Nguyen and Lostroh, 2013). We discovered that the core T6SS genes are not needed for a normal growth rate during exponential phase or for DNA release. However, we were unable to definitively determine if tssG, tssF, tssE, tssB, and tssC are necessary for survival during LTSP due to poor survival rates of the wild-type and mutants, likely caused by evaporation of water over the course of the experiments. Further research will be performed to determine which secretion system if any is responsible for DNA release and if tssG, tssF, tssE, tssB, and tssC are necessary for survival during LTSP.