1
|
Tierney ARP, Chin CY, Weiss DS, Rather PN. A LysR-Type Transcriptional Regulator Controls Multiple Phenotypes in Acinetobacter baumannii. Front Cell Infect Microbiol 2021; 11:778331. [PMID: 34805000 PMCID: PMC8601201 DOI: 10.3389/fcimb.2021.778331] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 10/14/2021] [Indexed: 12/03/2022] Open
Abstract
Acinetobacter baumannii is a multidrug-resistant, Gram-negative nosocomial pathogen that exhibits phenotypic heterogeneity resulting in virulent opaque (VIR-O) and avirulent translucent (AV-T) colony variants. Each variant has a distinct gene expression profile resulting in multiple phenotypic differences. Cells interconvert between the VIR-O and AV-T variants at high frequency under laboratory conditions, suggesting that the genetic mechanism underlying the phenotypic switch could be manipulated to attenuate virulence. Therefore, our group has focused on identifying and characterizing genes that regulate this switch, which led to the investigation of ABUW_1132 (1132), a highly conserved gene predicted to encode a LysR-type transcriptional regulator. ABUW_1132 was shown to be a global regulator as the expression of 74 genes was altered ≥ 2-fold in an 1132 deletion mutant. The 1132 deletion also resulted in a 16-fold decrease in VIR-O to AV-T switching, loss of 3-OH-C12-HSL secretion, and reduced surface-associated motility. Further, the deletion of 1132 in the AV-T background caused elevated capsule production, which increased colony opacity and altered the typical avirulent phenotype of translucent cells. These findings distinguish 1132 as a global regulatory gene and advance our understanding of A. baumannii’s opacity-virulence switch.
Collapse
Affiliation(s)
- Aimee R P Tierney
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA, United States
| | - Chui Yoke Chin
- Emory Vaccine Center, Atlanta, GA, United States.,Yerkes National Primate Research Center, Atlanta, GA, United States.,Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, United States.,Emory Antibiotic Resistance Center, Atlanta, GA, United States
| | - David S Weiss
- Emory Vaccine Center, Atlanta, GA, United States.,Yerkes National Primate Research Center, Atlanta, GA, United States.,Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, United States.,Emory Antibiotic Resistance Center, Atlanta, GA, United States.,Research Service, Department of Veterans Affairs, Atlanta Veterans Affairs (VA) Medical Center, Decatur, GA, United States
| | - Philip N Rather
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA, United States.,Research Service, Department of Veterans Affairs, Atlanta Veterans Affairs (VA) Medical Center, Decatur, GA, United States
| |
Collapse
|
2
|
De Silva PM, Patidar R, Graham CI, Brassinga AKC, Kumar A. A response regulator protein with antar domain, AvnR, in Acinetobacter baumannii ATCC 17978 impacts its virulence and amino acid metabolism. MICROBIOLOGY-SGM 2021; 166:554-566. [PMID: 32324528 DOI: 10.1099/mic.0.000913] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Acinetobacter baumannii, a Gram-negative coccobacillus, is notorious for its involvement in opportunistic infections around the world. Its resistance to antibiotics makes treatment of infections challenging. In this study, we describe a novel response regulator protein, AvnR (A1S_2006) that regulates virulence-related traits in A. baumannii ATCC17978. Sequence analysis suggests that AvnR is a CheY-like response regulator and contains the RNA-binding ANTAR (AmiR and NasR transcription anti-termination regulators) domain. We show that AvnR plays a role in regulating biofilm formation (on glass and plastic surfaces), surface motility, adhesion to A549 cells as well as in nitrogen metabolism in A. baumannii. RNA-Seq analysis revealed that avnR deletion results in altered expression of more than 150 genes (116 upregulated and 42 downregulated). RNA-Seq data suggest that altered biofilm formation and surface motility observed in the avnR deletion mutant is likely mediated by previously unknown pathways. Of note, was the altered expression of genes predicted to be involved in amino acid transport and metabolism in avnR deletion mutant. Biolog phenotypic array showed that deletion of avnR hampered A. baumannii ATCC17978's ability to metabolize various nitrogen sources, particularly that of glutamic acid, serine, histidine, aspartic acid, isoleucine and arginine. Taken together our data show that AvnR, the first ANTAR protein described in A. baumannii, affects virulence phenotypes as well as its ability to metabolize nitrogen sources.
Collapse
Affiliation(s)
- P Malaka De Silva
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada
| | - Rakesh Patidar
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada
| | | | | | | |
Collapse
|
3
|
New Shuttle Vectors for Real-Time Gene Expression Analysis in Multidrug-Resistant Acinetobacter Species: In Vitro and In Vivo Responses to Environmental Stressors. Appl Environ Microbiol 2019; 85:AEM.01334-19. [PMID: 31324623 DOI: 10.1128/aem.01334-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 07/06/2019] [Indexed: 11/20/2022] Open
Abstract
The Acinetobacter genus includes species of opportunistic pathogens and harmless saprophytes. The type species, Acinetobacter baumannii, is a nosocomial pathogen renowned for being multidrug resistant (MDR). Despite the clinical relevance of infections caused by MDR A. baumannii and a few other Acinetobacter spp., the regulation of their pathogenicity remains elusive due to the scarcity of adequate genetic tools, including vectors for gene expression analysis. Here, we report the generation and testing of a series of Escherichia coli-Acinetobacter promoter-probe vectors suitable for gene expression analysis in Acinetobacter spp. These vectors, named pLPV1Z, pLPV2Z, and pLPV3Z, carry both gentamicin and zeocin resistance markers and contain lux, lacZ, and green fluorescent protein (GFP) reporter systems downstream of an extended polylinker, respectively. The presence of a toxin-antitoxin gene system and the high copy number allow pLPV plasmids to be stably maintained even without antibiotic selection. The pLPV plasmids can easily be introduced by electroporation into MDR A. baumannii belonging to the major international lineages as well as into species of the Acinetobacter calcoaceticus-A. baumannii complex. The pLPV vectors have successfully been employed to study the regulation of stress-responsive A. baumannii promoters, including the DNA damage-inducible uvrABC promoter, the ethanol-inducible adhP and yahK promoters, and the iron-repressible promoter of the acinetobactin siderophore biosynthesis gene basA A lux-tagged A. baumannii ATCC 19606T strain, carrying the iron-responsive pLPV1Z::PbasA promoter fusion, allowed in vivo and ex vivo monitoring of the bacterial burden in the Galleria mellonella infection model.IMPORTANCE The short-term adaptive response to environmental cues greatly contributes to the ecological success of bacteria, and profound alterations in bacterial gene expression occur in response to physical, chemical, and nutritional stresses. Bacteria belonging to the Acinetobacter genus are ubiquitous inhabitants of soil and water though some species, such as Acinetobacter baumannii, are pathogenic and cause serious concern due to antibiotic resistance. Understanding A. baumannii pathobiology requires adequate genetic tools for gene expression analysis, and to this end we developed user-friendly shuttle vectors to probe the transcriptional responses to different environmental stresses. Vectors were constructed to overcome the problem of antibiotic selection in multidrug-resistant strains and were equipped with suitable reporter systems to facilitate signal detection. By means of these vectors, the transcriptional response of A. baumannii to DNA damage, ethanol exposure, and iron starvation was investigated both in vitro and in vivo, providing insights into A. baumannii adaptation during stress and infection.
Collapse
|
4
|
Ducas-Mowchun K, De Silva PM, Crisostomo L, Fernando DM, Chao TC, Pelka P, Schweizer HP, Kumar A. Next Generation of Tn 7-Based Single-Copy Insertion Elements for Use in Multi- and Pan-Drug-Resistant Strains of Acinetobacter baumannii. Appl Environ Microbiol 2019; 85:e00066-19. [PMID: 30902859 PMCID: PMC6532044 DOI: 10.1128/aem.00066-19] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 03/20/2019] [Indexed: 12/20/2022] Open
Abstract
The purpose of this study was to create single-copy gene expression systems for use in genomic manipulations of multidrug-resistant (MDR) and extensively drug-resistant (XDR) clinical isolates of Acinetobacter baumannii In this study, mini-Tn7 vectors with zeocin and apramycin selection markers were created by cloning the ble and aac(3)-IV genes, respectively, enabling either inducible gene expression (pUC18T-mini-Tn7T-Zeo-LAC and pUC18T-mini-Tn7T-Apr-LAC) or expression from native or constitutive promoters (pUC18T-mini-Tn7T-Zeo and pUC18T-mini-Tn7T-Apr). The selection markers of these plasmids are contained within a Flp recombinase target (FRT) cassette, which can be used to obtain unmarked mini-Tn7 insertions upon introduction of a source of Flp recombinase. To this end, site-specific excision vectors pFLP2A and pFLP2Z (containing apramycin and zeocin selection markers, respectively) were created in this study as an accessory to the mini-Tn7 vectors described above. Combinations of these novel mini-Tn7 plasmids and their compatible pFLP2Z or pFLP2A accessory plasmid were used to generate unmarked insertions in MDR clinical isolates of A. baumannii In addition, several fluorescent markers were cloned and inserted into MDR and XDR clinical isolates of A. baumannii via these apramycin and zeocin mini-Tn7 constructs to demonstrate their application.IMPORTANCEAcinetobacter baumannii is a high-priority pathogen for which research on mechanisms of resistance and virulence is a critical need. Commonly used antibiotic selection markers are not suitable for use in MDR and XDR isolates of A. baumannii due to the high antibiotic resistance of these isolates, which poses a barrier to the study of this pathogen. This study demonstrates the practical potential of using apramycin and zeocin mini-Tn7- and Flp recombinase-encoded constructs to carry out genomic manipulations in clinical isolates of A. baumannii displaying MDR and XDR phenotypes.
Collapse
Affiliation(s)
| | - P Malaka De Silva
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Leandro Crisostomo
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Dinesh M Fernando
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Tzu-Chiao Chao
- Department of Biology, University of Regina, Regina, Saskatchewan, Canada
| | - Peter Pelka
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Herbert P Schweizer
- University of Florida, College of Medicine, Department of Molecular Genetics and Microbiology, Emerging Pathogens Institute, Gainesville, Florida, USA
| | - Ayush Kumar
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
- Manitoba Chemosensory Biology Group, University of Manitoba, Winnipeg, Manitoba, Canada
| |
Collapse
|