Competence Dependent Chemotaxis and Genomic Repair in Acinetobacter baylyi

Overview

Acinetobacter baylyi, a gram-negative soil bacterium, is highly competent for natural transformation, a process in which DNA is imported across cellular membranes and potentially recombined into the chromosomal genome. This study evaluated the evolutionary roles of natural competence. Two studies were performed: twitching chemotaxis and genomic repair. Chemotaxis Experiment A chemotaxis assay was developed to investigate directional twitching towards DNA. Gradients were compared to static concentrations. Endogenous DNA was compared to exogenous DNA. Twitching chemotaxis was tested using a radial gradient method. Twitch distances along axes were measured. Two experimental setups were tested: an overnight test and a 6hr-overnight test. Data were analyzed using Paired T analysis. The noise within the data and high standard deviations stipulate further testing must be performed before drawing definitive conclusions; however it is unlikely that A. baylyi exhibits chemotaxis towards DNA. Genomic Repair Experiment A genomic repair experiment was devised to test whether competence aids survival of genomic damage. A collection of single gene deletion mutants was transformed into the local wild type background. Non-competent mutants lacking competence pilus proteins were compared to the wild type. A serial dilution series was performed. Cultures were exposed to UV radiation at 0 uJ, 50 uJ, 100 uJ, 150 uJ doses, then incubated overnight. Percent survival was calculated. Results were analyzed using One-Way ANOVA with Tukey post-hoc. The research hypothesis was unsupported. The three non-competent single gene deletion mutants did not exhibit decreased survival compared to the wild type. Thus it can be concluded competence does not aid in survival of UV damage.

Competition history

• ISEF 2015 Category not listed · Entry MCRO026I

Resources

• ISEF abstract page ↗

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