The sensor kinase BfmS controls production of outer membrane vesicles in Acinetobacter baumannii

Abstract

BackgroundAcinetobacter baumannii is an important opportunistic pathogen responsible for various nosocomial infections. The BfmRS two-component system plays a role in pathogenesis and antimicrobial resistance of A. baumannii via regulation of bacterial envelope structures. This study investigated the role of the sensor kinase, BfmS, in localization of outer membrane protein A (OmpA) in the outer membrane and production of outer membrane vesicles (OMVs) using wild-type A. baumannii ATCC 17978, ΔbfmS mutant, and bfmS-complemented strains.ResultsThe ΔbfmS mutant showed hypermucoid phenotype in the culture plates, growth retardation under static culture conditions, and reduced susceptibility to aztreonam and colistin compared to the wild-type strain. The ΔbfmS mutant produced less OmpA in the outer membrane but released more OmpA via OMVs than the wild-type strain, even though expression of ompA and its protein production were not different between the two strains. The ΔbfmS mutant produced 2.35 times more OMV particles and 4.46 times more OMV proteins than the wild-type stain. The ΔbfmS mutant OMVs were more cytotoxic towards A549 cells than wild-type strain OMVs.ConclusionsThe present study demonstrates that BfmS controls production of OMVs in A. baumannii. Moreover, BfmS negatively regulates antimicrobial resistance of A. baumannii and OMV-mediated host cell cytotoxicity. Our results indicate that BfmS negatively controls the pathogenic traits of A. baumannii via cell envelope structures and OMV production.

Mechanisms Protecting Acinetobacter baumannii against Multiple Stresses Triggered by the Host Immune Response, Antibiotics and Outside-Host Environment

“…The K locus is regulated by the two-component signal transduction system BfmRS. The global BfmR regulator, along with histidine kinase BfmS, controls a variety of processes, including biogenesis of A. baumannii envelope elements, formation of biofilms, desiccation tolerance, and multiple stress responses [ 46 , 47 , 48 , 49 ]. Several studies demonstrated that the production of capsules affects A. baumannii virulence and persistence in the host [ 50 , 51 ].…”

Study on RNA Regulating Iron Transport in Outer Membrane Vesicles of Hypervirulent Klebsiella Pneumoniae

“…OMVs are one of the research hotspots of microbial neighborhood in recent years, which are considered to be closely related to the virulence and pathogenicity of bacteria. In Acinetobacter baumannii, OMVs can provide more protection to the existing defense system under antibacterial pressure, and OMVmediated cytotoxicity of host cells and production of OMVs can be regulated by the BfmRS twocomponent system [10,11]. OMVs can also be produced by bacteria in internal and external environments, but the production of OMVs is a secretion process controlled by the environment [12], so different OMVs extraction methods have a certain impact on the number and content of OMVs.…”

Recent Advances in Genetic Tools for Acinetobacter baumannii

“…Electroporation into competent cells allows transposome entry ( Gallagher, 2019 ) however, this step cannot be easily performed in a high through-put manner leading to a preference for conjugation-based protocols ( Kazi et al, 2020 ). One vector-based Tn 5 systems also exist; pRL27 system in ATCC ® 17978 TM ( Kim et al, 2019 ) which can either be delivered to A. baumannii through electroporation or conjugation. Kim et al mutagenized ATCC ® 17978 TM and screened for loss of biofilm formation leading to the establishment of BfmRS two-component system’s role in outer membrane vesicle (OMV) production ( Kim et al, 2019 ).…”

“…One vector-based Tn 5 systems also exist; pRL27 system in ATCC ® 17978 TM ( Kim et al, 2019 ) which can either be delivered to A. baumannii through electroporation or conjugation. Kim et al mutagenized ATCC ® 17978 TM and screened for loss of biofilm formation leading to the establishment of BfmRS two-component system’s role in outer membrane vesicle (OMV) production ( Kim et al, 2019 ).…”

“…An antibiotic marker is engineered within the transposon that allows for the selection of a successful integration event. Currently tetracycline ( Pérez-Varela et al, 2020 ), kanamycin ( Gallagher et al, 2015 ; Hassan et al, 2016 ; Geisinger et al, 2019 ; Kazi et al, 2020 ; Sun et al, 2020 ), and a combination of kanamycin and chloramphenicol ( Kim et al, 2019 ; Lopez et al, 2020 ) are used during library generation in A. baumannii . These selection markers have been used in a variety of clinical isolates including AB5075, AbCAN2, BAL062, and AB0057 ( Supplementary Table 1 ).…”