A SIR2 family protein impacts biofilm formation by post-translational modifications in Acinetobacter baumannii

Acinetobacter baumannii is one of the most problematic opportunist pathogen responsible for many infections worldwide (1). Besides its high capacities to acquire antibiotic resistance mechanisms, it also presents high adhesion abilities on any types of abiotic or living surfaces leading to biofilm development, a mode of growth conferring an additional protection against various treatments and allowing the infection relapse (2). A. baumannii has been recently ranked on the global priority pathogens list established by the World Health Organization for which there is an urgent need for new treatments. One interesting way to identify new therapeutic targets to eradicate this pathogen is the characterization of its post-translational modifications (PTMs) (3). The functions and extents of PTMs remain largely unknown in prokaryotic cells compared to eukaryotic cells. Lysine acetylation is an attractive and prevalent PTM in bacteria. An increasing number of investigations have been dedicated to identify acetylated proteins by proteomics. Some studies have shown that acetylation can play a pivotal role in bacterial virulence, resistance, or biofilm (4). Enzymes involved in acetylation addition (lysine acetyltranferase KAT) or removal (lysine deacetylase KDAC) would provide a better mechanistic understanding of bacterial physiology and therefore could be considered as potential therapeutic targets. So far, little information is available on these enzymes in A. baumannii (5). Recently, in a global dynamic proteome study of A. baumannii ATCC 17978 strain grown in sessile mode, we highlighted the highest protein fold change for a protein belonging to the Sir2-like family which may possess a KDAC activity (6). The aim of the current study was to evaluate the involvement of this protein in A. baumannii physiology. For this purpose, a gene deletion approach was carried out to perform different phenotype tests (drugs and oxidative stress resistance, virulence assays, motility and biofilm formation) on wild-type and mutant strains. We compared, in biofilm mode of growth, acetylomes of the WT and the mutant. Our results demonstrated more than twice acetylated proteins in mutant in comparison to the WT. Of interest, biofilm formation in mutant was sensibly decreased. These different results suggest a potential involvement of this protein in A. baumannii biofilm formation.

 

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