Genes Unknown in Acinetobacter baumannii (GUNK)

GUNK logo

Program director: Samuel I. Miller MD, University of Washington

Investigators: Colin Manoil, Caroline S. Harwood, James E. Bruce, Mitchell J. Brittnacher, Hillary S. Hayden

Project home page:

Biological and web resources:

Project objectives: Acinetobacter baumannii is an emerging pathogen that causes primary and opportunistic infections, and is a serious concern in the hospital and battlefield settings. This organism has significant intrinsic resistance to antibiotics as well as an ability to quickly acquire new resistance. Additionally, A. baumannii can persist in a desiccated state on fomites, making disinfection and management of nosocomial infections particularly troublesome. The goal of the GUNK center is to find unexploited therapeutic approaches by elucidating the role of uncharacterized genes of A. baumannii in this organism’s mechanisms of pathogenesis, resistance, and persistence.

Resources for Genetic and Genomic Analysis of Emerging Pathogen Acinetobacter baumannii

Publication: PMC4438207

Acinetobacter baumannii is a Gram-negative bacterial pathogen notorious for causing serious nosocomial infections that resist antibiotic therapy. Research to identify factors responsible for the pathogen’s success has been limited by the resources available for genome-scale experimental studies. This report describes the development of several such resources for A. baumannii strain AB5075, a recently characterized wound isolate that is multidrug resistant and displays robust virulence in animal models. We report the completion and annotation of the genome sequence, the construction of a comprehensive ordered transposon mutant library, the extension of high-coverage transposon mutant pool sequencing (Tn-seq) to the strain, and the identification of the genes essential for growth on nutrient-rich agar. These resources should facilitate large-scale genetic analysis of virulence, resistance, and other clinically relevant traits that make A. baumannii a formidable public health threat.

Data sets and additional information can be found here.

Host-Microbe Protein Interactions during Bacterial Infection

Publication: PubMed PMID: 26548613

Interspecies protein-protein interactions are essential mediators of infection. While bacterial proteins required for host cell invasion and infection can be identified through bacterial mutant library screens, information about host target proteins and interspecies complex structures has been more difficult to acquire. Using an unbiased chemical crosslinking/mass spectrometry approach, we identified interspecies protein-protein interactions in human lung epithelial cells infected with Acinetobacter baumannii. These efforts resulted in identification of 3,076 crosslinked peptide pairs and 46 interspecies protein-protein interactions. Most notably, the key A. baumannii virulence factor, OmpA, was identified as crosslinked to host proteins involved in desmosomes, specialized structures that mediate host cell-to-cell adhesion. Co-immunoprecipitation and transposon mutant experiments were used to verify these interactions and demonstrate relevance for host cell invasion and acute murine lung infection. These results shed new light on A. baumannii-host protein interactions and their structural features, and the presented approach is generally applicable to other systems.

Data sets and additional information can be found here.

Joint Transcriptional Control of Virulence and Resistance to Antibiotic and Environmental Stress in Acinetobacter baumannii

Publication: PMC4532879

The increasing emergence of antibiotic-resistant bacterial pathogens represents a serious risk to human health and the entire health care system. Many currently circulating strains of Acinetobacter baumannii exhibit resistance to multiple antibiotics. A key limitation in combating A. baumannii is that our understanding of the molecular mechanisms underlying the pathogenesis of A. baumannii is lacking. To identify potential virulence determinants of a contemporary multidrug-resistant isolate of A. baumannii, we used transposon insertion sequencing (TnSeq) of strain AB5075. A collection of 250,000 A. baumannii transposon mutants was analyzed for growth within Galleria mellonella larvae, an insect-based infection model. The screen identified 300 genes that were specifically required for survival and/or growth of A. baumannii inside G. mellonella larvae. These genes encompass both known, established virulence factors and several novel genes. Among these were more than 30 transcription factors required for growth in G. mellonella. A subset of the transcription factors was also found to be required for resistance to antibiotics and environmental stress. This work thus establishes a novel connection between virulence and resistance to both antibiotics and environmental stress in A. baumannii.