Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

Small RNA-mediated regulation in Acinetobacter baumannii (#221)

Michael A Burch 1 , Ralf B Schittenhelm 2 , David Powell 3 , Marina Harper 1 , Anton Y Peleg 1 4 , Deanna Deveson Lucas 1 , John D Boyce 1
  1. Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Victoria, Australia
  2. Monash Biomedical Proteomics Facility, Biomedicine Discovery Institute and Department of Biochemistry & Molecular Biology, Monash University, Clayton, Victoria, Australia
  3. Monash Bioinformatics Platform, Monash University, Clayton, Victoria, Australia
  4. Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia

The Gram-negative bacterium Acinetobacter baumannii causes life-threatening nosocomial infections, and has a near unparalleled capacity to develop multidrug-resistance. Small non-coding RNAs (sRNAs) regulate bacterial physiology, antibiotic resistance, and virulence in many pathogens; however, there has been limited characterisation of these important regulatory molecules in A. baumannii. Bioinformatic analysis of multiple whole-transcriptome RNA-seq datasets identified more than 40 putative sRNAs that were highly conserved in strains AB5075, AB307-0294, ATCC 17978, and ATCC 19606; four of these sRNAs were selected for initial functional characterisation. Fluorescent primer extension analyses defined the transcriptional start sites of sRNA_2, sRNA_4, sRNA_61, and sRNA_74 in strain AB307-0294, strongly suggesting they were true sRNAs. Deletion mutants in each of the four sRNA genes were constructed and analysed via label-free quantitative proteomics to identify protein production changes compared to the wild-type AB307-0294 strain. Notably, all four sRNA mutants showed increased production of proteins in the same fimbrial biogenesis system, which is predicted to be involved in A. baumannii attachment and/or biofilm formation. In addition, the sRNA_2 mutant showed decreased production of proteins involved in D-amino acid metabolism, the sRNA_4 mutant showed decreased production of proteins involved in type IV pili assembly and function, and the sRNA_61 mutant showed increased production of a fibronectin-binding protein, which is predicted to be a key bacterial adhesin. Each of the sRNA mutants showed no significant change in growth or swarming motility, but the sRNA_4 mutant showed a statistically significant, although slight, reduction in biofilm formation. In conclusion, this study has shown that A. baumannii sRNAs may regulate key virulence-associated proteins, and thus sRNAs may be novel candidates for therapeutic targeting in strains of multidrug-resistant A. baumannii.