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Park SM, Suh JW, Ju YK, Kim JY, Kim SB, Sohn JW, Yoon YK. Molecular and virulence characteristics of carbapenem-resistant Acinetobacter baumannii isolates: a prospective cohort study. Sci Rep 2023; 13:19536. [PMID: 37945745 PMCID: PMC10636183 DOI: 10.1038/s41598-023-46985-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 11/07/2023] [Indexed: 11/12/2023] Open
Abstract
This study aimed to characterize the molecular features and virulence profiles of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates. Clinical CRAB isolates were obtained from blood cultures of adult patients with CRAB bacteremia, collected between July 2015 and July 2021 at a Korean hospital. Real-time polymerase chain reaction was used to detect 13 virulence genes, genotyping was conducted via multilocus sequence typing (MLST), and a Tenebrio molitor infection model was selected for survival analysis. Herein, 170 patients, from whom CRAB isolates were collected, showed the in-hospital mortality rate of 57.6%. All 170 clinical CRAB isolates harbored blaOXA-23 and blaOXA-51. MLST genotyping identified 11 CRAB sequence types (STs), of which ST191 was predominant (25.7%). Virulence genes were distributed as follows: basD, 58.9%; espA, 15.9%; bap, 92.4%; and ompA, 77.1%. In the T. molitor model, ST195 showed a significantly higher mortality rate (73.3% vs. 66.7%, p = 0.015) than the other groups. Our findings provide insights into the microbiological features of CRAB blood isolates associated with high mortality. We suggest a potential framework for using a T. molitor infection model to characterize CRAB virulence. Further research is warranted to elucidate the mechanisms by which virulence improves clinical outcomes.
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Affiliation(s)
- Seung Min Park
- Institute of Emerging Infectious Diseases, Korea University, Seoul, Republic of Korea
| | - Jin Woong Suh
- Division of Infectious Diseases, Department of Internal Medicine, Korea University Anam Hospital, Korea University College of Medicine, 73 Inchon-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Yong Kuk Ju
- Institute of Emerging Infectious Diseases, Korea University, Seoul, Republic of Korea
| | - Jeong Yeon Kim
- Division of Infectious Diseases, Department of Internal Medicine, Korea University Anam Hospital, Korea University College of Medicine, 73 Inchon-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Sun Bean Kim
- Division of Infectious Diseases, Department of Internal Medicine, Korea University Anam Hospital, Korea University College of Medicine, 73 Inchon-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Jang Wook Sohn
- Institute of Emerging Infectious Diseases, Korea University, Seoul, Republic of Korea
- Division of Infectious Diseases, Department of Internal Medicine, Korea University Anam Hospital, Korea University College of Medicine, 73 Inchon-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Young Kyung Yoon
- Institute of Emerging Infectious Diseases, Korea University, Seoul, Republic of Korea.
- Division of Infectious Diseases, Department of Internal Medicine, Korea University Anam Hospital, Korea University College of Medicine, 73 Inchon-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea.
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Fu S, Wang Q, Wang R, Zhang Y, Lan R, He F, Yang Q. Horizontal transfer of antibiotic resistance genes within the bacterial communities in aquacultural environment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 820:153286. [PMID: 35074363 DOI: 10.1016/j.scitotenv.2022.153286] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/13/2022] [Accepted: 01/16/2022] [Indexed: 06/14/2023]
Abstract
Very little is known about how microbiome interactions shape the horizontal transfer of antibiotic resistance genes in aquacultural environment. To this end, we first conducted 16S rRNA gene amplicon sequencing to monitor the dynamics of bacterial community compositions in one shrimp farm from 2019 to 2020. Next, co-occurrence analysis was then conducted to reveal the interactions network between Vibrio spp. and other species. Subsequently, 21 V. parahaemolyticus isolates and 15 related bacterial species were selected for whole-genome sequencing (WGS). The 16S rDNA amplicon sequencing results identified a remarkable increase of Vibrio and Providencia in September-2019 and a significant rise of Enterobacter and Shewanella in Septtember-2020. Co-occurrence analysis revealed that Vibrio spp. positively interacted with the above species, leading to the sequencing of their isolates to further understand the sharing of the resistant genomic islands (GIs). Subsequent pan-genomic analysis of V. parahaemolyticus genomes identified 278 horizontally transferred genes in 10 GIs, most of which were associated with antibiotic resistance, virulence, and fitness of metabolism. Most of the GIs have also been identified in Providencia, and Enterobacter, suggesting that exchange of genetic traits might occur in V. parahaemolyticus and other cooperative species in a specific niche. No genetic exchange was found between the species with negative relationships. The knowledge generated from this study would greatly improve our capacity to predict and mitigate the emergence of new resistant population and provide practical guidance on the microbial management during the aquacultural activities.
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Affiliation(s)
- Songzhe Fu
- College of Marine Science and Environment, Dalian Ocean University, Dalian, China.
| | - Qingyao Wang
- College of Marine Science and Environment, Dalian Ocean University, Dalian, China; Key Laboratory of Environment Controlled Aquaculture, Dalian Ocean University, Ministry of Education, 116023 Dalian, China
| | - Rui Wang
- College of Marine Science and Environment, Dalian Ocean University, Dalian, China; Key Laboratory of Environment Controlled Aquaculture, Dalian Ocean University, Ministry of Education, 116023 Dalian, China
| | - Yixiang Zhang
- CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Shanghai, China
| | - Ruiting Lan
- School of Biotechnology and Biomolecular Sciences, University of New South Wales (UNSW), Sydney, NSW, Australia
| | - Fenglan He
- The Collaboration Unit for Field Epidemiology of State Key Laboratory for Infectious Disease Prevention and Control, Nanchang Center for Disease Control and Prevention, Nanchang, China
| | - Qian Yang
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Gent, Belgium.
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Antipathogenic Compounds That Are Effective at Very Low Concentrations and Have Both Antibiofilm and Antivirulence Effects against Pseudomonas aeruginosa. Microbiol Spectr 2021; 9:e0024921. [PMID: 34494853 PMCID: PMC8557914 DOI: 10.1128/spectrum.00249-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Pseudomonas aeruginosa, a human pathogen, causes both acute and chronic infections that are mediated by virulence factor production and biofilm formation. Since both characteristics of P. aeruginosa are regulated by quorum sensing (QS), we screened 126 synthetic chemicals for anti-QS activity and finally selected the compounds that have both antivirulence and antibiofilm activities. To efficiently screen the chemical library, the following reporter-based bioassay systems were used: the QS- or biofilm-specific promoter-lacZ fusions (lasIp- or PA1897p-lacZ for the QS activity and cdrAp-lacZ for measuring the intracellular c-di-GMP levels). We also measured the production of virulence factors and biofilm formation in P. aeruginosa. A small-animal infection model using mealworms was also used for virulence analysis. From this screening, MHY1383 and MHY1387 were found to have both antivirulence and antibiofilm activities in P. aeruginosa. Most importantly, MHY1383 and MHY1387 exhibited these activities at very low concentrations, showing a significant anti-QS effect at 100 pM and an antibiofilm effect at 1 to 10 pM. By treating P. aeruginosa with these compounds, the virulence factor production and biofilm formation of P. aeruginosa were significantly reduced. These compounds can be developed as promising antipathogenic and antibiofilm drugs that can be applied in situations where such compounds must be used in an extremely low concentration. Our findings also offer a significant advantage for developing therapeutic agents with few adverse side effects. IMPORTANCE Many antibiotics are increasingly losing their efficacy due to antibiotic resistance mediated by biofilm formation. In this study, we screened a synthetic chemical library and discovered several compounds that have both antivirulence and antibiofilm effects against Pseudomonas aeruginosa, a notorious human pathogen. Two of them had these effects at extremely low concentrations and are expected not to develop resistance, unlike conventional antibiotics, because they have no effect on the growth of bacteria. Our results strongly suggest that these compounds act on the target in a noncompetitive manner, indicating that they are distinct from other previously known quorum sensing inhibitors or biofilm inhibitors. Our findings offer a significant advantage for developing therapeutic agents with few adverse side effects.
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Myszka K, Tomaś N, Wolko Ł, Szwengiel A, Grygier A, Nuc K, Majcher M. In situ approaches show the limitation of the spoilage potential of Juniperus phoenicea L. essential oil against cold-tolerant Pseudomonas fluorescens KM24. Appl Microbiol Biotechnol 2021; 105:4255-4268. [PMID: 33988734 PMCID: PMC8140959 DOI: 10.1007/s00253-021-11338-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 04/20/2021] [Accepted: 05/07/2021] [Indexed: 12/02/2022]
Abstract
Abstract The present study aimed to elucidate the effect of subinhibitory concentrations (sub-MICs) of juniper essential oil (EO), α-pinene, and sabinene on the quorum-sensing (QS)–mediated proteolytic and lipolytic properties of Pseudomonas fluorescens KM24. These activities were verified under in situ conditions, in which sub-MICs of the agents altered the morphology of KM24 cells. RNA-Seq studies revealed key coding sequences (CDSs)/genes related to QS and the proteolytic/lipolytic activities of pseudomonads. In this work, all the examined agents decreased autoinducer synthesis and influenced the mRNA expression of the encoding acyltransferase genes lptA, lptD, and plsB. The highest reduction on the 3rd and 5th days of cultivation was observed for the genes lptD (−5.5 and −5.61, respectively) and lptA (−3.5 and −4.0, respectively) following treatment with EO. Inhibition of the lptA, lptD, and plsB genes by singular constituents of EO was on average, from −0.4 to −0.7. At 5 days of cultivation the profile of AHLs of the reference P. fluorescens KM24 strain consisted of 3-oxo-C14-HSL, 3-oxo-C6-HSL, C4-HSL, and N-[(RS)-3-hydroxybutyryl]-HSL, the concentrations of which were 0.570, 0.018, 3.744, and 0.554 μg ml−1, respectively. Independent of the incubation time, EO, α-pinene, and sabinene also suppressed the protease genes prlC (−1.5, −0.5, and −0.5, respectively) and ctpB (−1.5, −0.7, and −0.4, respectively). Lipolysis and transcription of the lipA/lipB genes were downregulated by the agents on average from −0.3 to −0.6. α-Pinene- and sabinene-rich juniper EO acts as an anti-quorum-sensing agent and can repress the spoilage phenotype of pseudomonads. Key points: Juniper EO, α-pinene, sabinene exhibited anti-QS potential toward KM24. RNA-Seq revealed key CDSs/genes related to QS/proteolytic/lipolytic activities of KM24. Agents at sub-MIC levels influenced the mRNA expression of QS/lipase/protease genes.
Supplementary Information The online version contains supplementary material available at 10.1007/s00253-021-11338-3.
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Affiliation(s)
- Kamila Myszka
- Department of Biotechnology and Food Microbiology, Poznan University of Life Sciences, Wojska Polskiego 48, PL-60,627, Poznan, Poland.
| | - Natalia Tomaś
- Department of Biotechnology and Food Microbiology, Poznan University of Life Sciences, Wojska Polskiego 48, PL-60,627, Poznan, Poland
| | - Łukasz Wolko
- Department of Biochemistry and Biotechnology, Poznan University of Life Sciences, Dojazd 11, PL-60-632, Poznan, Poland
| | - Artur Szwengiel
- Department of Food Technology of Plant Origin, Poznan University of Life Sciences, Wojska Polskiego 31, PL-60-624, Poznan, Poland
| | - Anna Grygier
- Department of Food Technology of Plant Origin, Poznan University of Life Sciences, Wojska Polskiego 31, PL-60-624, Poznan, Poland
| | - Katarzyna Nuc
- Department of Biochemistry and Biotechnology, Poznan University of Life Sciences, Dojazd 11, PL-60-632, Poznan, Poland
| | - Małgorzata Majcher
- Department of Food Technology of Plant Origin, Poznan University of Life Sciences, Wojska Polskiego 31, PL-60-624, Poznan, Poland
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Post-secretional activation of Protease IV by quorum sensing in Pseudomonas aeruginosa. Sci Rep 2017; 7:4416. [PMID: 28667333 PMCID: PMC5493658 DOI: 10.1038/s41598-017-03733-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 05/02/2017] [Indexed: 11/08/2022] Open
Abstract
Protease IV (PIV), a key virulence factor of Pseudomonas aeruginosa is a secreted lysyl-endopeptidase whose expression is induced by quorum sensing (QS). We found that PIV expressed in QS mutant has severe reduction of activity in culture supernatant (CS), even though it is overexpressed to high level. PIV purified from the QS mutant (M-PIV) had much lower activity than the PIV purified from wild type (P-PIV). We found that the propeptide cleaved from prepro-PIV was co-purified with M-PIV, but never with P-PIV. Since the activity of M-PIV was restored by adding the CS of QS-positive and PIV-deficient strain, we hypothesized that the propeptide binds to and inhibits PIV, and is degraded to activate PIV by a QS-dependent factor. In fact, the CS of the QS-positive and PIV-deficient strain was able to degrade the propeptide. Since the responsible factor should be a QS-dependently expressed extracellular protease, we tested QS-dependent proteases of P. aeruginosa and found that LasB (elastase) can degrade the propeptide and activate M-PIV. We purified the propeptide of PIV and confirmed that the propeptide can bind to and inhibit PIV. We suggest that PIV is post-secretionally activated through the extracellular degradation of the propeptide by LasB, a QS-dependent protease.
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Comparative Genome Analyses of Vibrio anguillarum Strains Reveal a Link with Pathogenicity Traits. mSystems 2017; 2:mSystems00001-17. [PMID: 28293680 PMCID: PMC5347184 DOI: 10.1128/msystems.00001-17] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 01/30/2017] [Indexed: 01/30/2023] Open
Abstract
Comparative genome analysis of strains of a pathogenic bacterial species can be a powerful tool to discover acquisition of mobile genetic elements related to virulence. Here, we compared 28 V. anguillarum strains that differed in virulence in fish larval models. By pan-genome analyses, we found that six of nine highly virulent strains had a unique core and accessory genome. In contrast, V. anguillarum strains that were medium to nonvirulent had low genomic diversity. Integration of genomic and phenotypic features provides insights into the evolution of V. anguillarum and can also be important for survey and diagnostic purposes. Vibrio anguillarum is a marine bacterium that can cause vibriosis in many fish and shellfish species, leading to high mortalities and economic losses in aquaculture. Although putative virulence factors have been identified, the mechanism of pathogenesis of V. anguillarum is not fully understood. Here, we analyzed whole-genome sequences of a collection of V. anguillarum strains and compared them to virulence of the strains as determined in larval challenge assays. Previously identified virulence factors were globally distributed among the strains, with some genetic diversity. However, the pan-genome revealed that six out of nine high-virulence strains possessed a unique accessory genome that was attributed to pathogenic genomic islands, prophage-like elements, virulence factors, and a new set of gene clusters involved in biosynthesis, modification, and transport of polysaccharides. In contrast, V. anguillarum strains that were medium to nonvirulent had a high degree of genomic homogeneity. Finally, we found that a phylogeny based on the core genomes clustered the strains with moderate to no virulence, while six out of nine high-virulence strains represented phylogenetically separate clusters. Hence, we suggest a link between genotype and virulence characteristics of Vibrio anguillarum, which can be used to unravel the molecular evolution of V. anguillarum and can also be important from survey and diagnostic perspectives. IMPORTANCE Comparative genome analysis of strains of a pathogenic bacterial species can be a powerful tool to discover acquisition of mobile genetic elements related to virulence. Here, we compared 28 V. anguillarum strains that differed in virulence in fish larval models. By pan-genome analyses, we found that six of nine highly virulent strains had a unique core and accessory genome. In contrast, V. anguillarum strains that were medium to nonvirulent had low genomic diversity. Integration of genomic and phenotypic features provides insights into the evolution of V. anguillarum and can also be important for survey and diagnostic purposes.
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Castillo D, Christiansen RH, Dalsgaard I, Madsen L, Middelboe M. Bacteriophage resistance mechanisms in the fish pathogen Flavobacterium psychrophilum: linking genomic mutations to changes in bacterial virulence factors. Appl Environ Microbiol 2015; 81:1157-67. [PMID: 25480749 PMCID: PMC4292493 DOI: 10.1128/aem.03699-14] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 11/26/2014] [Indexed: 01/21/2023] Open
Abstract
Flavobacterium psychrophilum is an important fish pathogen in salmonid aquaculture worldwide. Due to increased antibiotic resistance, pathogen control using bacteriophages has been explored as a possible alternative treatment. However, the effective use of bacteriophages in pathogen control requires overcoming the selection for phage resistance in the bacterial populations. Here, we analyzed resistance mechanisms in F. psychrophilum after phage exposure using whole-genome sequencing of the ancestral phage-sensitive strain 950106-1/1 and six phage-resistant isolates. The phage-resistant strains had all obtained unique insertions and/or deletions and point mutations distributed among intergenic and genic regions. Mutations in genes related to cell surface properties, gliding motility, and biosynthesis of lipopolysaccharides and cell wall were found. The observed links between phage resistance and the genetic modifications were supported by direct measurements of bacteriophage adsorption rates, biofilm formation, and secretion of extracellular enzymes, which were all impaired in the resistant strains, probably due to superficial structural changes. The clustered regularly interspaced short palindromic repeat (CRISPR) region was unaffected in the resistant isolates and thus did not play a role as a resistance mechanism for F. psychrophilum under the current conditions. All together, the results suggest that resistance in F. psychrophilum was driven by spontaneous mutations, which were associated with a number of derived effects on the physiological properties of the pathogen, including reduced virulence under in vitro conditions. Consequently, phage-driven physiological changes associated with resistance may have implications for the impact of the pathogen in aquaculture, and these effects of phage resistance on host properties are therefore important for the ongoing exploration of phage-based control of F. psychrophilum.
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Affiliation(s)
- Daniel Castillo
- Marine Biological Section, University of Copenhagen, Helsingør, Denmark
| | - Rói Hammershaimb Christiansen
- Marine Biological Section, University of Copenhagen, Helsingør, Denmark National Veterinary Institute, Technical University of Denmark, Frederiksberg, Denmark
| | - Inger Dalsgaard
- National Veterinary Institute, Technical University of Denmark, Frederiksberg, Denmark
| | - Lone Madsen
- National Veterinary Institute, Technical University of Denmark, Frederiksberg, Denmark
| | - Mathias Middelboe
- Marine Biological Section, University of Copenhagen, Helsingør, Denmark
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Park SJ, Kim SK, So YI, Park HY, Li XH, Yeom DH, Lee MN, Lee BL, Lee JH. Protease IV, a quorum sensing-dependent protease of Pseudomonas aeruginosa modulates insect innate immunity. Mol Microbiol 2014; 94:1298-314. [PMID: 25315216 DOI: 10.1111/mmi.12830] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2014] [Indexed: 12/25/2022]
Abstract
In Pseudomonas aeruginosa, quorum sensing (QS) plays an essential role in pathogenesis and the QS response controls many virulence factors. Using a mealworm, Tenebrio molitor as a host model, we found that Protease IV, a QS-regulated exoprotease of P. aeruginosa functions as a key virulence effector causing the melanization and death of T. molitor larvae. Protease IV was able to degrade zymogens of spätzle processing enzyme (SPE) and SPE-activating enzyme (SAE) without the activation of the antimicrobial peptide (AMP) production. Since SPE and SAE function to activate spätzle, a ligand of Toll receptor in the innate immune system of T. molitor, we suggest that Protease IV may interfere with the activation of the Toll signaling. Independently of the Toll pathway, the melanization response, another innate immunity was still generated, since Protease IV directly converted Tenebrio prophenoloxidase into active phenoloxidase. Protease IV also worked as an important factor in the virulence to brine shrimp and nematode. These results suggest that Protease IV provides P. aeruginosa with a sophisticated way to escape the immune attack of host by interfering with the production of AMPs.
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Affiliation(s)
- Su-Jin Park
- College of Pharmacy, Pusan National University, Pusan, 609-735, Korea
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Quorum sensing-dependent metalloprotease VvpE is important in the virulence of Vibrio vulnificus to invertebrates. Microb Pathog 2014; 71-72:8-14. [DOI: 10.1016/j.micpath.2014.04.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 04/04/2014] [Accepted: 04/07/2014] [Indexed: 11/18/2022]
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10
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Yeom DH, Im SJ, Kim SK, Lee JH. Activation of multiple transcriptional regulators by growth restriction in Pseudomonas aeruginosa. Mol Cells 2014; 37:480-6. [PMID: 24938225 PMCID: PMC4086342 DOI: 10.14348/molcells.2014.0105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 05/22/2014] [Accepted: 05/23/2014] [Indexed: 11/29/2022] Open
Abstract
Growth restriction by antibiotics is a common feature that pathogenic bacteria must overcome for survival. The struggle of bacteria to escape from growth restriction eventually results in development of antibiotic-resistance through the expression of a set of genes. Here we found that some physiologically important transcriptional regulators of Pseudomonas aeruginosa including QscR, a quorum sensing (QS) receptor, SoxR, a superoxide sensor-regulator, and AntR, a regulator of anthranilate-related secondary metabolism, are activated by various growth-restricted conditions. We generated the growth-restricted conditions by various methods, such as overexpression of PA2537 and treatment with antibiotics or disinfectants. The overexpression of PA2537, encoding an acyltransferase homologue, tightly restricted the growth of P. aeruginosa and significantly activated QscR during the growth restriction. Similarly, treatments with gentamycin, tetracycline, and ethanol also activated QscR near their minimal inhibitory concentrations (MICs). Some non-QS regulators, such as AntR and SoxR, were also activated near the MICs in the same conditions. However, LasR and PqsR, other QS receptors of P. aeruginosa, were not activated, suggesting that only a specific set of transcriptional regulators is activated by growth restriction. Since paraquat, a super-oxide generator, significantly activated QscR and AntR, we suggest that the oxidative stress generated by growth restriction may be partly involved in this phenomenon.
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Affiliation(s)
- Doo Hwan Yeom
- Department of Pharmacy, College of Pharmacy, Pusan National University, Busan 609-735,
Korea
| | - Su-Jin Im
- Department of Pharmacy, College of Pharmacy, Pusan National University, Busan 609-735,
Korea
| | - Soo-Kyoung Kim
- Department of Pharmacy, College of Pharmacy, Pusan National University, Busan 609-735,
Korea
| | - Joon-Hee Lee
- Department of Pharmacy, College of Pharmacy, Pusan National University, Busan 609-735,
Korea
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