The abaI/abaR Quorum Sensing System Effects on Pathogenicity in Acinetobacter baumannii

Abstract

Acinetobacter baumannii is a Gram-negative pathogen that has emerged as one of the most troublesome pathogens for healthcare institutions globally. Bacterial quorum sensing (QS) is a process of cell-to-cell communication that relies on the production, secretion, and detection of autoinducer (AI) signals to share information about cell density and regulate gene expression accordingly. The molecular and genetic bases of A. baumannii virulence remains poorly understood. Therefore, the contribution of the abaI/abaR QS system to growth characteristics, morphology, biofilm formation, resistance, motility, and virulence of A. baumannii was studied in detail. RNA sequencing (RNA-seq) analysis indicated that genes involved in various aspects of energy production and conversion; valine, leucine, and isoleucine degradation; and lipid transport and metabolism are associated with bacterial pathogenicity. Our work provides a new insight into the abaI/abaR QS system effects on pathogenicity in A. baumannii. We propose that targeting the acyl homoserine lactone (AHL) synthase enzyme abaI could provide an effective strategy for attenuating virulence. On the contrary, interdicting the AI synthase receptor abaR elicits unpredictable consequences, which may lead to enhanced bacterial virulence.

Assessment of Antibiofilm Potencies of Nervonic and Oleic Acid against Acinetobacter baumannii Using In Vitro and Computational Approaches

“…AbaR functions as receptor protein for the AHL compound, and the binding induces a cascade of reactions [ 18 ]. The AbaI gene product AbaI is essential for A. baumannii biofilm formation and motility [ 13 , 14 , 17 ].…”

“…Recently, Tang et al (2020) reported that the AbaI gene of A. baumannii plays a major role in the development of antibiotic resistance [ 14 ]. Additionally, targeting the AHL synthase enzyme AbaI could provide an effective strategy for attenuating virulence in A. baumannii , whereas the receptor AbaR may show unpredictable consequences [ 17 ]. As AbaI produces AHLs by incorporating S-adenosyl methionine (SAM) and acyl–acyl carrier proteins [ 18 ], the active binding pocket of AbaI with SAM (a natural ligand to AbaI) may open new avenues for the scientific community to search for a QS inhibitor against A. baumannii.…”

Contribution of antimicrobial photo-sonodynamic therapy in wound healing: an in vivo effect of curcumin-nisin-based poly (L-lactic acid) nanoparticle on Acinetobacter baumannii biofilms

“…The production of pili which is required for the initial steps of biofilm formation and development of A. baumannii , is intermediated by the csuE [ 48 ]. Also, AbaI, encoded by abaI , as a quorum-sensing molecule that catalyzes the synthesis of AHL signals, is a required factor for the production of biofilm on abiotic surfaces [ 49 ]. In this study, there was a significant downregulation in abaI and csuE expression, as well as a considerable upregulation in blsA expression in A. baumannii during aPSDT SSR in comparison with the other groups.…”

Whole-Genome Sequencing of ST2 A. baumannii Causing Bloodstream Infections in COVID-19 Patients

“…The pathogenicity of A. baumannii isolates analyzed in the present study is exacerbated by the presence of the abaI / abaR quorum sensing system which is involved in morphology, growth characteristics, biofilm formation, motility, resistance and virulence of these microorganisms [ 36 ]. In addition, in our A. baumannii we found two-component signal transduction system BfmRS , which seem to be implicated in the control of various virulence-related traits and acting as a global modulator of A. baumannii physiology [ 37 , 38 ].…”