Phosphorylation of Extracellular Proteins in Acinetobacter baumannii in Sessile Mode of Growth.

Sébastien Massier,Pascal Cosette,Isabelle Broutin,Marina Harper,Emmanuelle Dé,Julie Hardouin,Brooke Hayes,Brandon Robin,Amy Wright,John D Boyce,Marianne Mégroz

doi:10.3389/fmicb.2021.738780

Abstract

Acinetobacter baumannii is a problematic nosocomial pathogen owing to its increasing resistance to antibiotics and its great ability to survive in the hospital environment, which is linked to its capacity to form biofilms. Structural and functional investigations of post-translational modifications, such as phosphorylations, may lead to identification of candidates for therapeutic targets against this pathogen. Here, we present the first S/T/Y phosphosecretome of two A. baumannii strains, the reference strain ATCC 17978 and the virulent multi-drug resistant strain AB0057, cultured in two modes of growth (planktonic and biofilm) using TiO2 chromatography followed by high resolution mass spectrometry. In ATCC 17978, we detected a total of 137 (97 phosphoproteins) and 52 (33 phosphoproteins) phosphosites in biofilm and planktonic modes of growth, respectively. Similarly, in AB0057, 155 (119 phosphoproteins) and 102 (74 phosphoproteins) phosphosites in biofilm and planktonic modes of growth were identified, respectively. Both strains in the biofilm mode of growth showed a higher number of phosphosites and phosphoproteins compared to planktonic growth. Several phosphorylated sites are localized in key regions of proteins involved in either drug resistance (β-lactamases), adhesion to host tissues (pilins), or protein secretion (Hcp). Site-directed mutagenesis of the Hcp protein, essential for type VI secretion system-mediated interbacterial competition, showed that four of the modified residues are essential for type VI secretion system activity.

Highlights

Acinetobacter baumannii is a Gram-negative nosocomial pathogen that mostly impacts patients in intensive care units and causes severe infections including pneumonia, bacteremia, endocarditis, skin and soft tissue infections, urinary tract infections, and meningitis (Bergogne-Bérézin and Towner, 1996; Dijkshoorn et al, 2007; Sengstock et al, 2010)
In order to identify phosphorylation events that occur during biofilm growth and determine those which may play important roles in bacterial virulence or resistance, we investigated the phospho-secretome of AB0057 in planktonic and biofilm modes of growth
Using a large-scale proteomic approach, we first assessed the phosphorylation of serine, threonine and tyrosine residues on extracellular proteins (S/T/Y phosphoproteomes) derived from biofilm and planktonic growth of A. baumannii reference strain ATCC 17978 and the virulent isolate AB0057

Summary

Introduction

Acinetobacter baumannii is a Gram-negative nosocomial pathogen that mostly impacts patients in intensive care units and causes severe infections including pneumonia, bacteremia, endocarditis, skin and soft tissue infections, urinary tract infections, and meningitis (Bergogne-Bérézin and Towner, 1996; Dijkshoorn et al, 2007; Sengstock et al, 2010). This organism has been recently classified by the WHO as "Critical" (Priority 1, together with P. aeruginosa and Enterobacteriaceae) in the list of global priority antibiotic-resistant bacteria, for which the research and development of Extracellular Phosphoproteins of A. baumannii Biofilm new and effective antibiotic treatments are urgently required. A. baumannii has an outstanding ability to adapt to detrimental environmental conditions

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Conclusion