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

Xiaoyu Sun,Zhaohui Ni,Yue Ding,Xinlei Wang,Fan Li,Jie Tang

doi:10.3389/fmicb.2021.679241

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.

Highlights

Acinetobacter baumannii is a Gram-negative, clinically important, opportunistic pathogen that causes a wide range of clinical infections
To test the role of the abaI/abaR quorum sensing (QS) system in the A. baumannii growth curve, we determined the optical density (OD) of the culture over time
The empty vector pME6032, used as a control, did not affect the growth profile of A. baumannii ATCC 17978 (Figure 1A). These results demonstrated that abaI affects the growth of A. baumannii

Summary

Introduction

Acinetobacter baumannii is a Gram-negative, clinically important, opportunistic pathogen that causes a wide range of clinical infections. Previous studies have emphasized the importance of iron acquisition, transports, cell-associated pili, lipopolysaccharides, and outer membrane proteins such as ompA, omp, and surA1 for virulence (Smani et al, 2013; Liu et al, 2016; Vila-Farres et al, 2017), but studies of quorum sensing (QS) effects on pathogenicity in A. baumannii are limited. Quorum Sensing System Effects Pathogenicity density and regulate gene expression (Rutherford and Bassler, 2012). AIs are involved in the regulation of varied biological functions, including expression of virulence gene in Vibrio cholerae (Herzog et al, 2019), Pseudomonas aeruginosa PAO1 (Li et al, 2017), Staphylococcus aureus (Kim M.K. et al, 2017), Escherichia coli (Zuo et al, 2019), and other bacteria (Miller and Bassler, 2001)

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