Masters Thesis

Natural Transformation in the Nosocomial Pathogen Acinetobacter Bauamnnii

Acinetobacter baumannii has emerged over the last few decades as a major nosocomial pathogen. Its ability to acquire genetic material and survive in extreme environments has positioned it as a paradigm of multidrug resistance. Horizontal genetic transfer, specifically natural transformation, has played a key role in its evolution. However, little is known about how competence for natural transformation is induced or regulated in A. baumannii and, therefore, our research focuses on identifying inducers of competence and characterizing genes involved in this process. to identify inducers of competence, A. baumannii cells were grown in the presence of host human products or antibiotics and transformation frequencies were assessed. Human serum albumin (HSA) was the only host human product that significantly increased transformation frequencies, suggesting that an albumin-specific mechanism exists in this species. in addition, all three antibiotics tested increased transformation frequencies, likely via different pathways. to better understand induction of competence, RNA sequencing was performed under HSA induction and 167 genes were identified as being significantly differentially expressed. Twenty-three genes were analyzed in depth, including putative transcriptional regulators and those associated with two component regulatory systems and type IV pili. This analysis led to the identification of a number of genes that were not explored before and whose roles in competence development are suitable for further analysis.

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