Acinetobacter baumannii is a Gram-negative opportunistic pathogen responsible for a range of nosocomial and community-acquired infections. The rapidly increasing prevalence of multi-drug resistant (MDR) A. baumannii strains, and other MDR bacterial pathogens, raises serious concerns about the availability of antimicrobial treatments for these organisms. Notably, many Gram-negative bacteria utilise a type VI secretion system (T6SS), which structurally resembles an inverted bacteriophage tail, to deliver toxic effector proteins directly into target cells. A. baumannii uses the T6SS to attack competing bacteria by delivering a diverse array of antibacterial effector proteins into nearby target cells. Preliminary work indicates that particular bacterial strains are susceptible to T6SS attack by the clinical isolate A. baumannii AB307-0294, whilst other strains are resistant. Immunity proteins are the most well characterised form of protection against T6SS-mediated killing. However, some bacteria are resistant to A. baumannii T6SS attack despite not encoding the specific immunity proteins required for protection, suggesting alternative defence mechanisms protect these strains. Additionally, our work indicates that A. baumannii AB307-0294 remains resistant to T6SS killing by sibling cells even when the required immunity genes are deleted, suggesting that A. baumannii AB307-0294 may utilise self-recognition to prevent attack of sibling cells. This study aims to identify the factors encoded within different prey strains that contribute to susceptibility/resistance to T6SS attack by A. baumannii AB307-0294. Further, we aim to identify whether self-recognition protects A. baumannii AB307-0294 from T6SS attack by sibling cells. Transposon Directed Insertion Sequencing (TraDIS) will be used to identify factors involved in self-recognition and the susceptibility/resistance of selected bacterial strains to attack by A. baumannii AB307-0294. Identification of cellular factors that affect the susceptibility/resistance of different bacteria to T6SS attack may enable this system to be redirected against specific pathogenic species in the future, providing a novel method of antimicrobial delivery.