1
|
Yin L, Wang Y, Xiang S, Xu K, Wang B, Jia AQ. Tyramine, one quorum sensing inhibitor, reduces pathogenicity and restores tetracycline susceptibility in Burkholderia cenocepacia. Biochem Pharmacol 2023; 218:115906. [PMID: 37951366 DOI: 10.1016/j.bcp.2023.115906] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 09/22/2023] [Accepted: 11/01/2023] [Indexed: 11/14/2023]
Abstract
Burkholderia cenocepacia is an opportunistic respiratory pathogen of particular relevance to patients with cystic fibrosis (CF), primarily regulating its biological functions and virulence factors through two quorum sensing (QS) systems (CepI/R and CciI/R). The highly persistent incidence of multidrug resistant Burkholderia cenocepacia poses a global threat to public health. In this study, we investigated the effects of tyramine, one biogenic amine, on the QS systems of Burkholderia cenocepacia. Genetic and biochemical analyses revealed that tyramine inhibited the production of N-hexanoyl-homoserine (AHL) signaling molecules (C8-HSL and C6-HSL) by blocking the CepI/R and CciI/R systems. As a result, the inhibition of QS systems leads to reduced production of various virulence factors, such as biofilm formation, extracellular polysaccharides, lipase, and swarming motility. Notably, as a potential quorum sensing inhibitor, tyramine exhibits low toxicity in vivo in Galleria mellonella larvae and is well characterized by Lipinski's five rules. It also shows high gastrointestinal absorption and the ability to cross the blood-brain barrier according to SwissADME database and ProTox-II server. Additionally, tyramine was found to enhance the efficacy of tetracycline in reducing the infectivity of Burkholderia cenocepacia in Galleria mellonella larvae infection model. Therefore, tyramine could be a promising candidate for combination therapy with traditional antimicrobials to improve their effectiveness against Burkholderia cenocepacia.
Collapse
Affiliation(s)
- Lujun Yin
- Hainan General Hospital, Hainan Affiliated Hospital of Hainan Medical University, Haikou 570311, China; Key Laboratory of Tropical Biological Resources of Ministry of Education, School of Pharmaceutical Sciences, Hainan University, Haikou 570228, China
| | - Yingjie Wang
- Key Laboratory of Tropical Biological Resources of Ministry of Education, School of Pharmaceutical Sciences, Hainan University, Haikou 570228, China
| | - Shiliang Xiang
- Key Laboratory of Tropical Biological Resources of Ministry of Education, School of Pharmaceutical Sciences, Hainan University, Haikou 570228, China
| | - Kaizhong Xu
- Key Laboratory of Tropical Biological Resources of Ministry of Education, School of Pharmaceutical Sciences, Hainan University, Haikou 570228, China
| | - Bo Wang
- Hainan General Hospital, Hainan Affiliated Hospital of Hainan Medical University, Haikou 570311, China
| | - Ai-Qun Jia
- Hainan General Hospital, Hainan Affiliated Hospital of Hainan Medical University, Haikou 570311, China.
| |
Collapse
|
2
|
Lami R, Urios L, Molmeret M, Grimaud R. Quorum sensing in biofilms: a key mechanism to target in ecotoxicological studies. Crit Rev Microbiol 2023; 49:786-804. [PMID: 36334083 DOI: 10.1080/1040841x.2022.2142089] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 10/18/2022] [Accepted: 10/26/2022] [Indexed: 11/06/2022]
Abstract
Our environment is heavily contaminated by anthropogenic compounds, and this issue constitutes a significant threat to all life forms, including biofilm-forming microorganisms. Cell-cell interactions shape microbial community structures and functions, and pollutants that affect intercellular communications impact biofilm functions and ecological roles. There is a growing interest in environmental science fields for evaluating how anthropogenic pollutants impact cell-cell interactions. In this review, we synthesize existing literature that evaluates the impacts of quorum sensing (QS), which is a widespread density-dependent communication system occurring within many bacterial groups forming biofilms. First, we examine the perturbating effects of environmental contaminants on QS circuits; and our findings reveal that QS is an essential yet underexplored mechanism affected by pollutants. Second, our work highlights that QS is an unsuspected and key resistance mechanism that assists bacteria in dealing with environmental contamination (caused by metals or organic pollutants) and that favors bacterial growth in unfavourable environments. We emphasize the value of considering QS a critical mechanism for monitoring microbial responses in ecotoxicology. Ultimately, we determine that QS circuits constitute promising targets for innovative biotechnological approaches with major perspectives for applications in the field of environmental science.
Collapse
Affiliation(s)
- Raphaël Lami
- Sorbonne Université, USR3579, LBBM, Observatoire Océanologique, Banyuls-sur-Mer, France
- Centre National de la Recherche Scientifique, USR 3579, LBBM, Observatoire Océanologique, Banyuls-sur-Mer, France
| | - Laurent Urios
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| | - Maëlle Molmeret
- Université de Toulon, Laboratoire MAPIEM, EA4323, Avenue de l'université, BP 20132, La Garde Cedex, France
| | - Régis Grimaud
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| |
Collapse
|
3
|
Hespanhol JT, Nóbrega-Silva L, Bayer-Santos E. Regulation of type VI secretion systems at the transcriptional, posttranscriptional and posttranslational level. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001376. [PMID: 37552221 PMCID: PMC10482370 DOI: 10.1099/mic.0.001376] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/25/2023] [Indexed: 08/09/2023]
Abstract
Bacteria live in complex polymicrobial communities and are constantly competing for resources. The type VI secretion system (T6SS) is a widespread antagonistic mechanism used by Gram-negative bacteria to gain an advantage over competitors. T6SSs translocate toxic effector proteins inside target prokaryotic cells in a contact-dependent manner. In addition, some T6SS effectors can be secreted extracellularly and contribute to the scavenging scarce metal ions. Bacteria deploy their T6SSs in different situations, categorizing these systems into offensive, defensive and exploitative. The great variety of bacterial species and environments occupied by such species reflect the complexity of regulatory signals and networks that control the expression and activation of the T6SSs. Such regulation is tightly controlled at the transcriptional, posttranscriptional and posttranslational level by abiotic (e.g. pH, iron) or biotic (e.g. quorum-sensing) cues. In this review, we provide an update on the current knowledge about the regulatory networks that modulate the expression and activity of T6SSs across several species, focusing on systems used for interbacterial competition.
Collapse
Affiliation(s)
- Julia Takuno Hespanhol
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Luize Nóbrega-Silva
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Ethel Bayer-Santos
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| |
Collapse
|
4
|
Recipient Cell Factors Influence Interbacterial Competition Mediated by Two Distinct Burkholderia dolosa Contact-Dependent Growth Inhibition Systems. J Bacteriol 2022; 204:e0054121. [PMID: 36000834 PMCID: PMC9487645 DOI: 10.1128/jb.00541-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Contact-dependent growth inhibition (CDI) systems mediate interbacterial antagonism between Gram-negative bacteria by delivering the toxic portion of a large surface protein (termed BcpA in Burkholderia species) to the cytoplasm of neighboring bacteria. Translocation of the antibacterial polypeptide into recipient cells requires specific recipient outer and inner membrane proteins, but the identity of these factors outside several model organisms is unknown. To identify genes involved in CDI susceptibility in the Burkholderia cepacia complex member Burkholderia dolosa, a transposon mutagenesis selection approach was used to enrich for mutants resistant to BcpA-1 or BcpA-2. Subsequent analysis showed that candidate regulatory genes contributed modestly to recipient cell susceptibility to B. dolosa CDI. However, most candidate deletion mutants did not show the same phenotypes as the corresponding transposon mutants. Whole-genome resequencing revealed that these transposon mutants also contained unique mutations within a three gene locus (wabO, BDAG_01006, and BDAG_01005) encoding predicted lipopolysaccharide (LPS) biosynthesis enzymes. B. dolosa wabO, BDAG_01006, or BDAG_01005 mutants were resistant to CDI and produced LPS with altered core oligosaccharide and O-antigen. Although BcpA-1 and BcpA-2 are dissimilar and expected to utilize different outer membrane receptors, intoxication by both proteins was similarly impacted by LPS changes. Together, these findings suggest that alterations in cellular regulation may indirectly impact the efficiency of CDI-mediated competition and demonstrate that LPS is required for intoxication by two distinct B. dolosa BcpA proteins. IMPORTANCEContact-dependent growth inhibition (CDI) system proteins, produced by many Gram-negative bacteria, are narrow spectrum antimicrobials that inhibit the growth of closely related neighboring bacteria. Here, we use the opportunistic pathogen Burkholderia dolosa to identify genes required for intoxication by two distinct CDI system proteins. Our findings suggest that B. dolosa recipient cells targeted by CDI systems are only intoxicated if they produce full-length lipopolysaccharide. Understanding the mechanisms underlying antagonistic interbacterial interactions may contribute to future therapeutic development.
Collapse
|
5
|
Dennehy R, Duggan N, Dignam S, McCormack S, Dillon E, Molony J, Romano M, Hou Y, Ardill L, Whelan MVX, Drulis‐Kawa Z, Ó'Cróinín T, Valvano MA, Berisio R, McClean S. Protein with negative surface charge distribution, Bnr1, shows characteristics of a DNA-mimic protein and may be involved in the adaptation of Burkholderia cenocepacia. Microbiologyopen 2022; 11:e1264. [PMID: 35212475 PMCID: PMC9060813 DOI: 10.1002/mbo3.1264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/14/2022] [Indexed: 11/11/2022] Open
Abstract
Adaptation of opportunistic pathogens to their host environment requires reprogramming of a vast array of genes to facilitate survival in the host. Burkholderia cenocepacia, a Gram-negative bacterium with a large genome of ∼8 Mb that colonizes environmental niches, is exquisitely adaptable to the hypoxic environment of the cystic fibrosis lung and survives in macrophages. We previously identified an immunoreactive acidic protein encoded on replicon 3, BCAS0292. Deletion of the BCAS0292 gene significantly altered the abundance of 979 proteins by 1.5-fold or more; 19 proteins became undetectable while 545 proteins showed ≥1.5-fold reduced abundance, suggesting the BCAS0292 protein is a global regulator. Moreover, the ∆BCAS0292 mutant showed a range of pleiotropic effects: virulence and host-cell attachment were reduced, antibiotic susceptibility was altered, and biofilm formation enhanced. Its growth and survival were impaired in 6% oxygen. In silico prediction of its three-dimensional structure revealed BCAS0292 presents a dimeric β-structure with a negative surface charge. The ΔBCAS0292 mutant displayed altered DNA supercoiling, implicated in global regulation of gene expression. Three proteins were identified in pull-downs with FLAG-tagged BCAS0292, including the Histone H1-like protein, HctB, which is recognized as a global transcriptional regulator. We propose that BCAS0292 protein, which we have named Burkholderia negatively surface-charged regulatory protein 1 (Bnr1), acts as a DNA-mimic and binds to DNA-binding proteins, altering DNA topology and regulating the expression of multiple genes, thereby enabling the adaptation of B. cenocepacia to highly diverse environments.
Collapse
Affiliation(s)
- Ruth Dennehy
- Centre of Microbial Host InteractionsInstitute of Technology TallaghtDublinIreland
| | - Niamh Duggan
- School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway Institute of Biomolecular and Biomedical ResearchUniversity College DublinBelfield, DublinIreland
| | - Simon Dignam
- Centre of Microbial Host InteractionsInstitute of Technology TallaghtDublinIreland
| | - Sarah McCormack
- School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway Institute of Biomolecular and Biomedical ResearchUniversity College DublinBelfield, DublinIreland
| | - Eugene Dillon
- UCD Conway Institute of Biomolecular and Biomedical ResearchUniversity College DublinBelfield, DublinIreland
| | - Jessica Molony
- School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
| | - Maria Romano
- Institute of Biostructures and BioimagingNational Research CouncilNaplesItaly
| | - Yueran Hou
- School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway Institute of Biomolecular and Biomedical ResearchUniversity College DublinBelfield, DublinIreland
| | - Laura Ardill
- School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
| | - Matthew V. X. Whelan
- School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
| | - Zuzanna Drulis‐Kawa
- Department of Pathogen Biology and Immunology, Institute of Genetics and MicrobiologyUniversity of WroclawWroclawPoland
| | - Tadhg Ó'Cróinín
- School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
| | - Miguel A. Valvano
- School of Medicine, Dentistry and Biomedical Sciences, Wellcome‐Wolfson Institute for Experimental MedicineQueen's University BelfastBelfastUK
| | - Rita Berisio
- Institute of Biostructures and BioimagingNational Research CouncilNaplesItaly
| | - Siobhán McClean
- Centre of Microbial Host InteractionsInstitute of Technology TallaghtDublinIreland
- School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway Institute of Biomolecular and Biomedical ResearchUniversity College DublinBelfield, DublinIreland
| |
Collapse
|
6
|
Metabolomic profiling of Burkholderia cenocepacia in synthetic cystic fibrosis sputum medium reveals nutrient environment-specific production of virulence factors. Sci Rep 2021; 11:21419. [PMID: 34725378 PMCID: PMC8560942 DOI: 10.1038/s41598-021-00421-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 10/12/2021] [Indexed: 12/13/2022] Open
Abstract
Infections by Burkholderia cenocepacia lead to life-threatening disease in immunocompromised individuals, including those living with cystic fibrosis (CF). While genetic variation in various B. cenocepacia strains has been reported, it remains unclear how the chemical environment of CF lung influences the production of small molecule virulence factors by these strains. Here we compare metabolomes of three clinical B. cenocepacia strains in synthetic CF sputum medium (SCFM2) and in a routine laboratory medium (LB), in the presence and absence of the antibiotic trimethoprim. Using a mass spectrometry-based untargeted metabolomics approach, we identify several compound classes which are differentially produced in SCFM2 compared to LB media, including siderophores, antimicrobials, quorum sensing signals, and various lipids. Furthermore, we describe that specific metabolites are induced in the presence of the antibiotic trimethoprim only in SCFM2 when compared to LB. Herein, C13-acyl-homoserine lactone, a quorum sensing signal previously not known to be produced by B. cenocepacia as well as pyochelin-type siderophores were exclusively detected during growth in SCFM2 in the presence of trimethoprim. The comparative metabolomics approach described in this study provides insight into environment-dependent production of secondary metabolites by B. cenocepacia strains and suggests future work which could identify personalized strain-specific regulatory mechanisms involved in production of secondary metabolites. Investigations into whether antibiotics with different mechanisms of action induce similar metabolic alterations will inform development of combination treatments aimed at effective clearance of Burkholderia spp. pathogens.
Collapse
|
7
|
Bidirectional Cell-Cell Communication via Indole and Cyclo(Pro-Tyr) Modulates Interspecies Biofilm Formation. Appl Environ Microbiol 2021; 87:e0127721. [PMID: 34469193 DOI: 10.1128/aem.01277-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The extracellular signaling molecule indole plays a pivotal role in biofilm formation by the enteric gammaproteobacterium Escherichia coli; this process is particularly correlated with the extracellular indole concentration. Using the indole-biodegrading betaproteobacterium Burkholderia unamae, we examined the mechanism by which these two bacteria modulate biofilm formation in an indole-dependent manner. We quantified the spatial organization of cocultured microbial communities at the micrometer scale through computational image analysis, ultimately identifying how bidirectional cell-to-cell communication modulated the physical relationships between them. Further analysis allowed us to determine the mechanism by which the B. unamae-derived signaling diketopiperazine cyclo(Pro-Tyr) considerably upregulated indole biosynthesis and enhanced E. coli biofilm formation. We also determined that the presence of unmetabolized indole enhanced the production of cyclo(Pro-Tyr). Thus, bidirectional cell-to-cell communication that occurred via interspecies signaling molecules modulated the formation of a mixed-species biofilm between indole-producing and indole-consuming species. IMPORTANCE Indole is a relatively stable N-heterocyclic aromatic compound that is widely found in nature. To date, the correlations between indole-related bidirectional cell-to-cell communications and interspecies communal organization remain poorly understood. In this study, we used an experimental model, which consisted of indole-producing and indole-degrading bacteria, to evaluate how bidirectional cell-to-cell communication modulated interspecies biofilm formation via intrinsic and environmental cues. We identified a unique spatial patterning of indole-producing and indole-degrading bacteria within mixed-species biofilms. This spatial patterning was an active process mediated by bidirectional physicochemical interactions. Our findings represent an important step in gaining a more thorough understanding of the process of polymicrobial biofilm formation and advance the possibility of using indole-degrading bacteria to address biofilm-related health and industry issues.
Collapse
|
8
|
Zeng YH, Cheng KK, Cai ZH, Zhu JM, Du XP, Wang Y, Zhou J. Transcriptome analysis expands the potential roles of quorum sensing in biodegradation and physiological responses to microcystin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 771:145437. [PMID: 33736182 DOI: 10.1016/j.scitotenv.2021.145437] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/08/2021] [Accepted: 01/22/2021] [Indexed: 06/12/2023]
Abstract
Bacterial degradation is one of the most efficient ways to remove microcystins (MCs), the most frequently detected toxin in cyanobacterial blooms. Using Novosphingobium sp. ERW19 as a representative strain, our laboratory previously demonstrated that quorum sensing (QS), the cell density-dependent gene regulation system, positively regulates biodegradation of MCs via transcriptional activation of mlr-pathway-associated genes. Increasing evidence indicates that QS is involved in a wide spectrum of regulatory circuits, but it remains unclear which physiological processes in MC degradation besides the expression of MC-degrading genes are also subject to QS-dependent regulation. This study used transcriptome analysis to identify QS-regulated genes during degradation of MCs. A large percentage (up to 32.6%) of the genome of the MC-degrading bacterial strain Novosphingobium sp. ERW19 was significantly differentially expressed in the corresponding QS mutants. Pathway enrichment analysis of QS-regulated genes revealed that QS mainly influenced metabolism-associated pathways, particularly those related to amino acid metabolism, carbohydrate metabolism, and biodegradation and metabolism of xenobiotics. In-depth functional interpretation of QS-regulated genes indicated a variety of pathways were potentially associated with bacterial degradation or physiological responses to MCs, including genes involved in cell motility, cytochrome P450-dependent metabolism of xenobiotics, glutathione S-transferase (GST), envelope stress response, and ribosomes. Furthermore, QS may be involved in regulating the initial and final steps of the catabolic pathway of phenylacetic acid, an intermediate product of MC degradation. Collectively, this global survey of QS-regulated genes in a MC-degrading bacterial strain facilitates a deeper understanding of QS-controlled processes that may be important for bacterial degradation of MCs or may contribute to the physiological responses of bacteria to MCs.
Collapse
Affiliation(s)
- Yan-Hua Zeng
- Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China; Institute for Ocean Engineering, Tsinghua University, Beijing 100084, PR China
| | - Ke-Ke Cheng
- Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China; Institute for Ocean Engineering, Tsinghua University, Beijing 100084, PR China
| | - Zhong-Hua Cai
- Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China; Institute for Ocean Engineering, Tsinghua University, Beijing 100084, PR China
| | - Jian-Ming Zhu
- Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China
| | - Xiao-Peng Du
- Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China
| | - Yan Wang
- Shenzhen Polytechnic, Shenzhen 518055, PR China.
| | - Jin Zhou
- Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China; Institute for Ocean Engineering, Tsinghua University, Beijing 100084, PR China.
| |
Collapse
|
9
|
Shropshire H, Jones RA, Aguilo-Ferretjans MM, Scanlan DJ, Chen Y. Proteomics insights into the Burkholderia cenocepacia phosphorus stress response. Environ Microbiol 2021; 23:5069-5086. [PMID: 33684254 DOI: 10.1111/1462-2920.15451] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 03/02/2021] [Indexed: 11/26/2022]
Abstract
The Burkholderia cepacia complex is a group of Burkholderia species that are opportunistic pathogens causing high mortality rates in patients with cystic fibrosis. An environmental stress often encountered by these soil-dwelling and pathogenic bacteria is phosphorus limitation, an essential element for cellular processes. Here, we describe cellular and extracellular proteins differentially regulated between phosphate-deplete (0 mM, no added phosphate) and phosphate-replete (1 mM) growth conditions using a comparative proteomics (LC-MS/MS) approach. We observed a total of 128 and 65 unique proteins were downregulated and upregulated respectively, in the B. cenocepacia proteome. Of those downregulated proteins, many have functions in amino acid transport/metabolism. We have identified 24 upregulated proteins that are directly/indirectly involved in inorganic phosphate or organic phosphorus acquisition. Also, proteins involved in virulence and antimicrobial resistance were differentially regulated, suggesting B. cenocepacia experiences a dramatic shift in metabolism under these stress conditions. Overall, this study provides a baseline for further research into the biology of Burkholderia in response to phosphorus stress.
Collapse
Affiliation(s)
- Holly Shropshire
- BBSRC Midlands Integrative Biosciences Training Partnership, University of Warwick, Coventry, CV4 7AL, UK.,School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Rebekah A Jones
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | | | - David J Scanlan
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Yin Chen
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| |
Collapse
|
10
|
ScmR, a Global Regulator of Gene Expression, Quorum Sensing, pH Homeostasis, and Virulence in Burkholderia thailandensis. J Bacteriol 2020; 202:JB.00776-19. [PMID: 32312745 DOI: 10.1128/jb.00776-19] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 04/13/2020] [Indexed: 11/20/2022] Open
Abstract
The nonpathogenic soil saprophyte Burkholderia thailandensis is a member of the Burkholderia pseudomallei /B. thailandensis/B. mallei group, which also comprises the closely related human pathogens B. pseudomallei and Burkholderia mallei responsible for the melioidosis and glanders diseases, respectively. ScmR, a recently identified LysR-type transcriptional regulator in B. thailandensis, acts as a global transcriptional regulator throughout the stationary phase and modulates the production of a wide range of secondary metabolites, including N-acyl-l-homoserine lactones and 4-hydroxy-3-methyl-2-alkylquinolines and virulence in the Caenorhabditis elegans nematode worm host model, as well as several quorum sensing (QS)-dependent phenotypes. We have investigated the role of ScmR in B. thailandensis strain E264 during the exponential phase. We used RNA sequencing transcriptomic analyses to identify the ScmR regulon, which was compared to the QS-controlled regulon, showing a considerable overlap between the ScmR-regulated genes and those controlled by QS. We characterized several genes modulated by ScmR using quantitative reverse transcription-PCR or mini-CTX-lux transcriptional reporters, including the oxalate biosynthetic gene obc1 required for pH homeostasis, the orphan LuxR-type transcriptional regulator BtaR5-encoding gene, and the bsa (Burkholderia secretion apparatus) type III secretion system genes essential for both B. pseudomallei and B. mallei pathogenicity, as well as the scmR gene itself. We confirmed that the transcription of scmR is under QS control, presumably ensuring fine-tuned modulation of gene expression. Finally, we demonstrated that ScmR influences virulence using the fruit fly model host Drosophila melanogaster We conclude that ScmR represents a central component of the B. thailandensis QS regulatory network.IMPORTANCE Coordination of the expression of genes associated with bacterial virulence and environmental adaptation is often dependent on quorum sensing (QS). The QS circuitry of the nonpathogenic bacterium Burkholderia thailandensis, widely used as a model system for the study of the human pathogen Burkholderia pseudomallei, is complex. We found that the LysR-type transcriptional regulator, ScmR, which is highly conserved and involved in the control of virulence/survival factors in the Burkholderia genus, is a global regulator mediating gene expression through the multiple QS systems coexisting in B. thailandensis, as well as QS independently. We conclude that ScmR represents a key QS modulatory network element, ensuring tight regulation of the transcription of QS-controlled genes, particularly those required for acclimatization to the environment.
Collapse
|
11
|
Phenylacetyl Coenzyme A, Not Phenylacetic Acid, Attenuates CepIR-Regulated Virulence in Burkholderia cenocepacia. Appl Environ Microbiol 2019; 85:AEM.01594-19. [PMID: 31585996 DOI: 10.1128/aem.01594-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 09/30/2019] [Indexed: 11/20/2022] Open
Abstract
During phenylalanine catabolism, phenylacetic acid (PAA) is converted to phenylacetyl coenzyme A (PAA-CoA) by a ligase, PaaK, and then PAA-CoA is epoxidized by a multicomponent monooxygenase, PaaABCDE, before further degradation through the tricarboxylic acid (TCA) cycle. In the opportunistic pathogen Burkholderia cenocepacia, loss of paaABCDE attenuates virulence factor expression, which is under the control of the LuxIR-like quorum sensing (QS) system, CepIR. To further investigate the link between CepIR-regulated virulence and PAA catabolism, we created knockout mutants of the first step of the pathway (PAA-CoA synthesis by PaaK) and characterized them in comparison to a paaABCDE mutant using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and virulence assays. We found that while loss of PaaABCDE decreased virulence, deletion of the paaK genes resulted in a more virulent phenotype than that of the wild-type strain. Deletion of either paaK or paaABCDE led to higher levels of released PAA but no differences in levels of internal accumulation compared to the wild-type level. While we found no evidence of direct cepIR downregulation by PAA-CoA or PAA, a low-virulence cepR mutant reverted to a virulent phenotype upon removal of the paaK genes. On the other hand, removal of paaABCDE in the cepR mutant did not impact its attenuated phenotype. Together, our results suggest an indirect role for PAA-CoA in suppressing B. cenocepacia CepIR-activated virulence.IMPORTANCE The opportunistic pathogen Burkholderia cenocepacia uses a chemical signal process called quorum sensing (QS) to produce virulence factors. In B. cenocepacia, QS relies on the presence of the transcriptional regulator CepR which, upon binding QS signal molecules, activates virulence. In this work, we found that even in the absence of CepR, B. cenocepacia can elicit a pathogenic response if phenylacetyl-CoA, an intermediate of the phenylacetic acid degradation pathway, is not produced. Instead, accumulation of phenylacetyl-CoA appears to attenuate pathogenicity. Therefore, we have discovered that it is possible to trigger virulence in the absence of CepR, challenging the classical view of activation of virulence by this QS mechanism. Our work provides new insight into the relationship between metabolism and virulence in opportunistic bacteria. We propose that in the event that QS signaling molecules cannot accumulate to trigger a pathogenic response, a metabolic signal can still activate virulence in B. cenocepacia.
Collapse
|
12
|
Oppy CC, Jebeli L, Kuba M, Oates CV, Strugnell R, Edgington-Mitchell LE, Valvano MA, Hartland EL, Newton HJ, Scott NE. Loss of O-Linked Protein Glycosylation in Burkholderia cenocepacia Impairs Biofilm Formation and Siderophore Activity and Alters Transcriptional Regulators. mSphere 2019; 4:e00660-19. [PMID: 31722994 PMCID: PMC6854043 DOI: 10.1128/msphere.00660-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 10/24/2019] [Indexed: 02/07/2023] Open
Abstract
O-linked protein glycosylation is a conserved feature of the Burkholderia genus. The addition of the trisaccharide β-Gal-(1,3)-α-GalNAc-(1,3)-β-GalNAc to membrane exported proteins in Burkholderia cenocepacia is required for bacterial fitness and resistance to environmental stress. However, the underlying causes of the defects observed in the absence of glycosylation are unclear. Using proteomics, luciferase reporter assays, and DNA cross-linking, we demonstrate the loss of glycosylation leads to changes in transcriptional regulation of multiple proteins, including the repression of the master quorum CepR/I. These proteomic and transcriptional alterations lead to the abolition of biofilm formation and defects in siderophore activity. Surprisingly, the abundance of most of the known glycosylated proteins did not significantly change in the glycosylation-defective mutants, except for BCAL1086 and BCAL2974, which were found in reduced amounts, suggesting they could be degraded. However, the loss of these two proteins was not responsible for driving the proteomic alterations, biofilm formation, or siderophore activity. Together, our results show that loss of glycosylation in B. cenocepacia results in a global cell reprogramming via alteration of the transcriptional regulatory systems, which cannot be explained by the abundance changes in known B. cenocepacia glycoproteins.IMPORTANCE Protein glycosylation is increasingly recognized as a common posttranslational protein modification in bacterial species. Despite this commonality, our understanding of the role of most glycosylation systems in bacterial physiology and pathogenesis is incomplete. In this work, we investigated the effect of the disruption of O-linked glycosylation in the opportunistic pathogen Burkholderia cenocepacia using a combination of proteomic, molecular, and phenotypic assays. We find that in contrast to recent findings on the N-linked glycosylation systems of Campylobacter jejuni, O-linked glycosylation does not appear to play a role in proteome stabilization of most glycoproteins. Our results reveal that loss of glycosylation in B. cenocepacia strains leads to global proteome and transcriptional changes, including the repression of the quorum-sensing regulator cepR (BCAM1868) gene. These alterations lead to dramatic phenotypic changes in glycosylation-null strains, which are paralleled by both global proteomic and transcriptional alterations, which do not appear to directly result from the loss of glycosylation per se. This research unravels the pleiotropic effects of O-linked glycosylation in B. cenocepacia, demonstrating that its loss does not simply affect the stability of the glycoproteome, but also interferes with transcription and the broader proteome.
Collapse
Affiliation(s)
- Cameron C Oppy
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Victoria, Australia
| | - Leila Jebeli
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Miku Kuba
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Clare V Oates
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Richard Strugnell
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Laura E Edgington-Mitchell
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Victoria, Australia
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
- Department of Oral and Maxillofacial Surgery, New York University College of Dentistry, Bluestone Center for Clinical Research, New York, New York, USA
| | - Miguel A Valvano
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, United Kingdom
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Elizabeth L Hartland
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Victoria, Australia
- Department of Molecular and Translational Science, Monash University, Clayton, Victoria, Australia
| | - Hayley J Newton
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Nichollas E Scott
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| |
Collapse
|
13
|
Hogan AM, Rahman ASMZ, Lightly TJ, Cardona ST. A Broad-Host-Range CRISPRi Toolkit for Silencing Gene Expression in Burkholderia. ACS Synth Biol 2019; 8:2372-2384. [PMID: 31491085 DOI: 10.1021/acssynbio.9b00232] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Genetic tools are critical to dissecting the mechanisms governing cellular processes, from fundamental physiology to pathogenesis. Members of the genus Burkholderia have potential for biotechnological applications but can also cause disease in humans with a debilitated immune system. The lack of suitable genetic tools to edit Burkholderia GC-rich genomes has hampered the exploration of useful capacities and the understanding of pathogenic features. To address this, we have developed CRISPR interference (CRISPRi) technology for gene silencing in Burkholderia, testing it in B. cenocepacia, B. multivorans, and B. thailandensis. Tunable expression was provided by placing a codon-optimized dcas9 from Streptococcus pyogenes under control of a rhamnose-inducible promoter. As a proof of concept, the paaABCDE operon controlling genes necessary for phenylacetic acid degradation was targeted by plasmid-borne gRNAs, resulting in near complete inhibition of growth on phenylacetic acid as the sole carbon source. This was supported by reductions in paaA mRNA expression. The utility of CRISPRi to probe other functions at the single cell level was demonstrated by knocking down phbC and fliF, which dramatically reduces polyhydroxybutyrate granule accumulation and motility, respectively. As a hallmark of the mini-CTX system is the broad host-range of integration, we putatively identified 67 genera of Proteobacteria that might be amenable to modification with our CRISPRi toolkit. Our CRISPRi toolkit provides a simple and rapid way to silence gene expression to produce an observable phenotype. Linking genes to functions with CRISPRi will facilitate genome editing with the goal of enhancing biotechnological capabilities while reducing Burkholderia's pathogenic arsenal.
Collapse
Affiliation(s)
- Andrew M Hogan
- Department of Microbiology , University of Manitoba , Winnipeg , Manitoba R3T 2N2 , Canada
| | - A S M Zisanur Rahman
- Department of Microbiology , University of Manitoba , Winnipeg , Manitoba R3T 2N2 , Canada
| | - Tasia J Lightly
- Department of Microbiology , University of Manitoba , Winnipeg , Manitoba R3T 2N2 , Canada
| | - Silvia T Cardona
- Department of Microbiology , University of Manitoba , Winnipeg , Manitoba R3T 2N2 , Canada
- Department of Medical Microbiology & Infectious Diseases , University of Manitoba , Winnipeg , Manitoba R3T 2N2 , Canada
| |
Collapse
|
14
|
Quorum Sensing as Antivirulence Target in Cystic Fibrosis Pathogens. Int J Mol Sci 2019; 20:ijms20081838. [PMID: 31013936 PMCID: PMC6515091 DOI: 10.3390/ijms20081838] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 04/11/2019] [Accepted: 04/11/2019] [Indexed: 12/17/2022] Open
Abstract
Cystic fibrosis (CF) is an autosomal recessive genetic disorder which leads to the secretion of a viscous mucus layer on the respiratory epithelium that facilitates colonization by various bacterial pathogens. The problem of drug resistance has been reported for all the species able to colonize the lung of CF patients, so alternative treatments are urgently needed. In this context, a valid approach is to investigate new natural and synthetic molecules for their ability to counteract alternative pathways, such as virulence regulating quorum sensing (QS). In this review we describe the pathogens most commonly associated with CF lung infections: Staphylococcus aureus, Pseudomonas aeruginosa, species of the Burkholderia cepacia complex and the emerging pathogens Stenotrophomonas maltophilia, Haemophilus influenzae and non-tuberculous Mycobacteria. For each bacterium, the QS system(s) and the molecules targeting the different components of this pathway are described. The amount of investigations published in the last five years clearly indicate the interest and the expectations on antivirulence therapy as an alternative to classical antibiotics.
Collapse
|
15
|
Liao H, Zhong X, Xu L, Ma Q, Wang Y, Cai Y, Guo X. Quorum-sensing systems trigger catalase expression to reverse the oxyR deletion-mediated VBNC state in Salmonella typhimurium. Res Microbiol 2019; 170:65-73. [DOI: 10.1016/j.resmic.2018.10.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 10/26/2018] [Accepted: 10/29/2018] [Indexed: 11/24/2022]
|
16
|
Two rsaM Homologues Encode Central Regulatory Elements Modulating Quorum Sensing in Burkholderia thailandensis. J Bacteriol 2018; 200:JB.00727-17. [PMID: 29507087 DOI: 10.1128/jb.00727-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 02/20/2018] [Indexed: 01/05/2023] Open
Abstract
The bacterium Burkholderia thailandensis possesses three N-acyl-l-homoserine lactone (AHL) quorum sensing (QS) systems designated BtaI1/BtaR1 (QS-1), BtaI2/BtaR2 (QS-2), and BtaI3/BtaR3 (QS-3). These QS systems are associated with the biosynthesis of N-octanoyl-homoserine lactone (C8-HSL), N-3-hydroxy-decanoyl-homoserine lactone (3OHC10-HSL), and N-3-hydroxy-octanoyl-homoserine lactone (3OHC8-HSL), which are produced by the LuxI-type synthases BtaI1, BtaI2, and BtaI3 and modulated by the LuxR-type transcriptional regulators BtaR1, BtaR2, and BtaR3. The btaR1-btaI1 and btaR2-btaI2 gene clusters each carry an additional gene encoding a homologue of the QS repressor RsaM originally identified in the phytopathogen Pseudomonas fuscovaginae and thus here named rsaM1 and rsaM2, respectively. We have characterized the functions of these two conserved rsaM homologues and demonstrated their involvement in the regulation of AHL biosynthesis in B. thailandensis strain E264. We quantified the production of C8-HSL, 3OHC10-HSL, and 3OHC8-HSL by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in the wild-type strain and in the rsaM1 and rsaM2 mutants, and we monitored btaI1, btaI2, and btaI3 expression using chromosomal mini-CTX-lux transcriptional reporters. The transcription of btaR1, btaR2, and btaR3 was also measured by quantitative reverse transcription-PCR (qRT-PCR). We observed that RsaM1 mainly represses the QS-1 system, whereas RsaM2 principally represses the QS-2 system. We also found that both rsaM1 and rsaM2 are QS controlled and negatively autoregulated. We conclude that RsaM1 and RsaM2 are an integral part of the QS circuitry of B. thailandensis and play a major role in the hierarchical and homeostatic organization of the QS-1, QS-2, and QS-3 systems.IMPORTANCE Quorum sensing (QS) is commonly involved in the coordination of gene transcription associated with the establishment of host-pathogen interactions and acclimatization to the environment. We present the functional characterization of two rsaM homologues in the regulation of the multiple QS systems coexisting in the nonpathogenic bacterium Burkholderia thailandensis, which is widely used as a model system for the study of the human pathogen Burkholderia pseudomallei We found that inactivation of these rsaM homologues, which are clustered with the other QS genes, profoundly affects the QS circuitry of B. thailandensis We conclude that they constitute essential regulatory components of the QS modulatory network and provide additional layers of regulation to modulate the transcription of QS-controlled genes, particularly those linked to environmental adaptation.
Collapse
|
17
|
Wong YC, Abd El Ghany M, Ghazzali RNM, Yap SJ, Hoh CC, Pain A, Nathan S. Genetic Determinants Associated With in Vivo Survival of Burkholderia cenocepacia in the Caenorhabditis elegans Model. Front Microbiol 2018; 9:1118. [PMID: 29896180 PMCID: PMC5987112 DOI: 10.3389/fmicb.2018.01118] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Accepted: 05/11/2018] [Indexed: 12/15/2022] Open
Abstract
A Burkholderia cenocepacia infection usually leads to reduced survival and fatal cepacia syndrome in cystic fibrosis patients. The identification of B. cenocepacia essential genes for in vivo survival is key to designing new anti-infectives therapies. We used the Transposon-Directed Insertion Sequencing (TraDIS) approach to identify genes required for B. cenocepacia survival in the model infection host, Caenorhabditis elegans. A B. cenocepacia J2315 transposon pool of ∼500,000 mutants was used to infect C. elegans. We identified 178 genes as crucial for B. cenocepacia survival in the infected nematode. The majority of these genes code for proteins of unknown function, many of which are encoded by the genomic island BcenGI13, while other gene products are involved in nutrient acquisition, general stress responses and LPS O-antigen biosynthesis. Deletion of the glycosyltransferase gene wbxB and a histone-like nucleoid structuring (H-NS) protein-encoding gene (BCAL0154) reduced bacterial accumulation and attenuated virulence in C. elegans. Further analysis using quantitative RT-PCR indicated that BCAL0154 modulates B. cenocepacia pathogenesis via transcriptional regulation of motility-associated genes including fliC, fliG, flhD, and cheB1. This screen has successfully identified genes required for B. cenocepacia survival within the host-associated environment, many of which are potential targets for developing new antimicrobials.
Collapse
Affiliation(s)
- Yee-Chin Wong
- School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Malaysia
| | - Moataz Abd El Ghany
- Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.,The Westmead Institute for Medical Research and The Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Sydney, NSW, Australia
| | - Raeece N M Ghazzali
- Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | | | | | - Arnab Pain
- Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Sheila Nathan
- School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Malaysia
| |
Collapse
|
18
|
Quorum-sensing control of antibiotic resistance stabilizes cooperation in Chromobacterium violaceum. ISME JOURNAL 2018; 12:1263-1272. [PMID: 29374267 DOI: 10.1038/s41396-018-0047-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 12/08/2017] [Accepted: 12/21/2017] [Indexed: 01/10/2023]
Abstract
Many Proteobacteria use quorum sensing to regulate production of public goods, such as antimicrobials and proteases, that are shared among members of a community. Public goods are vulnerable to exploitation by cheaters, such as quorum sensing-defective mutants. Quorum sensing- regulated private goods, goods that benefit only producing cells, can prevent the emergence of cheaters under certain growth conditions. Previously, we developed a laboratory co-culture model to investigate the importance of quorum-regulated antimicrobials during interspecies competition. In our model, Burkholderia thailandensis and Chromobacterium violaceum each use quorum sensing-controlled antimicrobials to inhibit the other species' growth. Here, we show that C. violaceum uses quorum sensing to increase resistance to bactobolin, a B. thailandensis antibiotic, by increasing transcription of a putative antibiotic efflux pump. We demonstrate conditions where C. violaceum quorum-defective cheaters emerge and show that in these conditions, bactobolin restrains cheaters. We also demonstrate that bactobolin restrains quorum-defective mutants in our co-culture model, and the increase in antimicrobial-producing cooperators drives the C. violaceum population to become more competitive. Our results describe a mechanism of cheater restraint involving quorum control of efflux pumps and demonstrate that interspecies competition can reinforce cooperative behaviors by placing constraints on quorum sensing-defective mutants.
Collapse
|
19
|
Slachmuylders L, Van Acker H, Brackman G, Sass A, Van Nieuwerburgh F, Coenye T. Elucidation of the mechanism behind the potentiating activity of baicalin against Burkholderia cenocepacia biofilms. PLoS One 2018; 13:e0190533. [PMID: 29293658 PMCID: PMC5749847 DOI: 10.1371/journal.pone.0190533] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 12/16/2017] [Indexed: 11/19/2022] Open
Abstract
Reduced antimicrobial susceptibility due to resistance and tolerance has become a serious threat to human health. An approach to overcome this reduced susceptibility is the use of antibiotic adjuvants, also known as potentiators. These are compounds that have little or no antibacterial effect on their own but increase the susceptibility of bacterial cells towards antimicrobial agents. Baicalin hydrate, previously described as a quorum sensing inhibitor, is such a potentiator that increases the susceptibility of Burkholderia cenocepacia J2315 biofilms towards tobramycin. The goal of the present study is to elucidate the molecular mechanisms behind the potentiating activity of baicalin hydrate and related flavonoids. We first determined the effect of multiple flavonoids on susceptibility of B. cenocepacia J2315 towards tobramycin. Increased antibiotic susceptibility was most pronounced in combination with apigenin 7-O-glucoside and baicalin hydrate. For baicalin hydrate, also other B. cepacia complex strains and other antibiotics were tested. The potentiating effect was only observed for aminoglycosides and was both strain- and aminoglycoside-dependent. Subsequently, gene expression was compared between baicalin hydrate treated and untreated cells, in the presence and absence of tobramycin. This revealed that baicalin hydrate affected cellular respiration, resulting in increased reactive oxygen species production in the presence of tobramycin. We subsequently showed that baicalin hydrate has an impact on oxidative stress via several pathways including oxidative phosphorylation, glucarate metabolism and by modulating biosynthesis of putrescine. Furthermore, our data strongly suggest that the influence of baicalin hydrate on oxidative stress is unrelated to quorum sensing. Our data indicate that the potentiating effect of baicalin hydrate is due to modulating the oxidative stress response, which in turn leads to increased tobramycin-mediated killing.
Collapse
Affiliation(s)
- Lisa Slachmuylders
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Heleen Van Acker
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Gilles Brackman
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Andrea Sass
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | | | - Tom Coenye
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
- * E-mail:
| |
Collapse
|
20
|
Chapalain A, Groleau MC, Le Guillouzer S, Miomandre A, Vial L, Milot S, Déziel E. Interplay between 4-Hydroxy-3-Methyl-2-Alkylquinoline and N-Acyl-Homoserine Lactone Signaling in a Burkholderia cepacia Complex Clinical Strain. Front Microbiol 2017; 8:1021. [PMID: 28676791 PMCID: PMC5476693 DOI: 10.3389/fmicb.2017.01021] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 05/22/2017] [Indexed: 11/13/2022] Open
Abstract
Species from the Burkholderia cepacia complex (Bcc) share a canonical LuxI/LuxR quorum sensing (QS) regulation system named CepI/CepR, which mainly relies on the acyl-homoserine lactone (AHL), octanoyl-homoserine lactone (C8-HSL) as signaling molecule. Burkholderia ambifaria is one of the least virulent Bcc species, more often isolated from rhizospheres where it exerts a plant growth-promoting activity. However, clinical strains of B. ambifaria display distinct features, such as phase variation and higher virulence properties. Notably, we previously reported that under laboratory conditions, only clinical strains of the B. ambifaria species produced 4-hydroxy-3-methyl-2-alkylquinolines (HMAQs) via expression of the hmqABCDEFG operon. HMAQs are the methylated counterparts of the 4-hydroxy-2-alkylquinolines (HAQs) produced by the opportunistic human pathogen Pseudomonas aeruginosa, in which they globally contribute to the bacterial virulence and survival. We have found that unlike P. aeruginosa's HAQs, HMAQs do not induce their own production. However, they indirectly regulate the expression of the hmqABCDEFG operon. In B. ambifaria, a strong link between CepI/CepR-based QS and HMAQs is proposed, as we have previously reported an increased production of C8-HSL in HMAQ-negative mutants. Here, we report the identification of all AHLs produced by the clinical B. ambifaria strain HSJ1, namely C6-HSL, C8-HSL, C10-HSL, 3OHC8-HSL, 3OHC10-HSL, and 3OHC12-HSL. Production of significant levels of hydroxylated AHLs prompted the identification of a second complete LuxI/LuxR-type QS system relying on 3OHC10-HSL and 3OHC12-HSL, that we have named CepI2/CepR2. The connection between these two QS systems and the hmqABCDEFG operon, responsible for HMAQs biosynthesis, was investigated. The CepI/CepR system strongly induced the operon, while the second system appears moderately involved. On the other hand, a HMAQ-negative mutant overproduces AHLs from both QS systems. Even if HMAQs are not classical QS signals, their effect on AHL-based QS system still gives them a part to play in the QS circuitry in B. ambifaria and thus, on regulation of various phenotypes.
Collapse
Affiliation(s)
- Annelise Chapalain
- CIRI, Centre International de Recherche en Infectiologie, Equipe Pathogénèse des Légionelles, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, École Normale Supérieure de Lyon, Université LyonLyon, France
| | | | | | - Aurélie Miomandre
- CNRS, INRA, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
| | - Ludovic Vial
- CNRS, INRA, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
| | | | - Eric Déziel
- INRS-Institut Armand-Frappier, LavalQC, Canada
| |
Collapse
|
21
|
Burkholderia cepacia Complex Regulation of Virulence Gene Expression: A Review. Genes (Basel) 2017; 8:genes8010043. [PMID: 28106859 PMCID: PMC5295037 DOI: 10.3390/genes8010043] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/11/2017] [Accepted: 01/12/2017] [Indexed: 12/31/2022] Open
Abstract
Burkholderia cepacia complex (Bcc) bacteria emerged as opportunistic pathogens in cystic fibrosis and immunocompromised patients. Their eradication is very difficult due to the high level of intrinsic resistance to clinically relevant antibiotics. Bcc bacteria have large and complex genomes, composed of two to four replicons, with variable numbers of insertion sequences. The complexity of Bcc genomes confers a high genomic plasticity to these bacteria, allowing their adaptation and survival to diverse habitats, including the human host. In this work, we review results from recent studies using omics approaches to elucidate in vivo adaptive strategies and virulence gene regulation expression of Bcc bacteria when infecting the human host or subject to conditions mimicking the stressful environment of the cystic fibrosis lung.
Collapse
|
22
|
Nunvar J, Kalferstova L, Bloodworth RAM, Kolar M, Degrossi J, Lubovich S, Cardona ST, Drevinek P. Understanding the Pathogenicity of Burkholderia contaminans, an Emerging Pathogen in Cystic Fibrosis. PLoS One 2016; 11:e0160975. [PMID: 27512997 PMCID: PMC4981469 DOI: 10.1371/journal.pone.0160975] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 07/27/2016] [Indexed: 12/22/2022] Open
Abstract
Several bacterial species from the Burkholderia cepacia complex (Bcc) are feared opportunistic pathogens that lead to debilitating lung infections with a high risk of developing fatal septicemia in cystic fibrosis (CF) patients. However, the pathogenic potential of other Bcc species is yet unknown. To elucidate clinical relevance of Burkholderia contaminans, a species frequently isolated from CF respiratory samples in Ibero-American countries, we aimed to identify its key virulence factors possibly linked with an unfavorable clinical outcome. We performed a genome-wide comparative analysis of two isolates of B. contaminans ST872 from sputum and blood culture of a female CF patient in Argentina. RNA-seq data showed significant changes in expression for quorum sensing-regulated virulence factors and motility and chemotaxis. Furthermore, we detected expression changes in a recently described low-oxygen-activated (lxa) locus which encodes stress-related proteins, and for two clusters responsible for the biosynthesis of antifungal and hemolytic compounds pyrrolnitrin and occidiofungin. Based on phenotypic assays that confirmed changes in motility and in proteolytic, hemolytic and antifungal activities, we were able to distinguish two phenotypes of B. contaminans that coexisted in the host and entered her bloodstream. Whole genome sequencing revealed that the sputum and bloodstream isolates (each representing a distinct phenotype) differed by over 1,400 mutations as a result of a mismatch repair-deficient hypermutable state of the sputum isolate. The inferred lack of purifying selection against nonsynonymous mutations and the high rate of pseudogenization in the derived isolate indicated limited evolutionary pressure during evolution in the nutrient-rich, stable CF sputum environment. The present study is the first to examine the genomic and transcriptomic differences between longitudinal isolates of B. contaminans. Detected activity of a number of putative virulence factors implies a genuine pathogenic nature of this novel Bcc species.
Collapse
Affiliation(s)
- Jaroslav Nunvar
- Department of Medical Microbiology, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czech Republic
| | - Lucie Kalferstova
- Department of Medical Microbiology, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czech Republic
| | - Ruhi A. M. Bloodworth
- Department of Medical Microbiology & Infectious Disease, University of Manitoba, Winnipeg, Canada
| | - Michal Kolar
- Laboratory of Genomics and Bioinformatics, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Jose Degrossi
- School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina
| | - Silvina Lubovich
- Centro Respiratorio Dr. A. Alvarez, Hospital de Niños Ricardo Gutiérrez, Buenos Aires, Argentina
| | - Silvia T. Cardona
- Department of Medical Microbiology & Infectious Disease, University of Manitoba, Winnipeg, Canada
| | - Pavel Drevinek
- Department of Medical Microbiology, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czech Republic
- * E-mail:
| |
Collapse
|
23
|
Veselova MA, Romanova YM, Lipasova VA, Koksharova OA, Zaitseva YV, Chernukha MU, Gintsburg AL, Khmel IA. The effect of mutation in the clpX gene on the synthesis of N-acyl-homoserine lactones and other properties of Burkholderia cenocepacia 370. Microbiol Res 2016; 186-187:90-8. [PMID: 27242147 DOI: 10.1016/j.micres.2016.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 03/24/2016] [Accepted: 03/31/2016] [Indexed: 10/22/2022]
Abstract
In order to study the regulation of N-acyl-homoserine lactones synthesis (AHLs, the signal molecules of Quorum Sensing regulation) in Burkholderia cenocepacia strain 370 we obtained mutants with increased AHL production. One of the mutants, named BC-B6, was obtained by TnMod-RKm(r) plasposon mutagenesis. The plasposon insertion was located within the clpX gene encoding the ATPase subunit ClpX of the ClpXP protease. The mutation reduced bacterial virulence in mice intranasal infection. The results of proteomic analysis demonstrated that the expression of at least 19 proteins differed not less than 2-fold between the parental and mutant strains. 18 of the proteins were upregulated in the mutant, and one protein was downregulated. The proteins included those that involved in protein synthesis and modification, in energy production, in general metabolism, in transport and regulation. To check the effect of the clpX mutation on the AHL synthesis, a mutant with inactivated clpX gene (BC-clpX:Km(r)) was constructed by gene replacement method. This mutant also exhibited increased AHLs production. A swarming motility of both mutants was reduced compared to the original strain. Thus, the obtained results show that the clpX gene was involved in the regulation of AHL production and a number of cellular processes in B. cenocepacia 370.
Collapse
Affiliation(s)
- M A Veselova
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 2, Moscow 123182, Russia
| | - Yu M Romanova
- The Gamaleya Scientific Research Centre of Epidemiology and Microbiology, Gamaleya Str. 18, Moscow 123098, Russia
| | - V A Lipasova
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 2, Moscow 123182, Russia
| | - O A Koksharova
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 2, Moscow 123182, Russia; M.V. Lomonosov Moscow State University, A.N. Belozersky Institute of Physico-Chemical Biology, Leninskie Gory 1-40, Moscow 119991, Russia
| | - Yu V Zaitseva
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 2, Moscow 123182, Russia
| | - M U Chernukha
- The Gamaleya Scientific Research Centre of Epidemiology and Microbiology, Gamaleya Str. 18, Moscow 123098, Russia
| | - A L Gintsburg
- The Gamaleya Scientific Research Centre of Epidemiology and Microbiology, Gamaleya Str. 18, Moscow 123098, Russia
| | - I A Khmel
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 2, Moscow 123182, Russia.
| |
Collapse
|
24
|
Van Acker H, De Canck E, Van Nieuwerburgh F, Sass A, Deforce D, Nelis HJ, Coenye T. The BCESM genomic region contains a regulator involved in quorum sensing and persistence in Burkholderia cenocepacia J2315. Future Microbiol 2014; 9:845-60. [DOI: 10.2217/fmb.14.54] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
ABSTRACT: Aim: In this study, we investigated the function of BCAM0257-8-9 located in the BCESM region of the Burkholderia cenocepacia J2315 genome. Materials & methods: Differential RNA sequencing was used to determine transcription start sites. The phenotype of overexpression mutants was studied and a transcriptome analysis of the BCAM0258 overexpression mutant was performed. Results: BCAM0257 and BCAM0258 were identified as belonging to an operon, positively regulated by BCAM0259. We found that this operon is involved in persistence and that BCAM0258 functions as a regulator influencing quorum sensing and activating pathways related to iron acquisition and biofilm formation. Overexpression of BCAM0257 increased virulence. Conclusion: The BCESM genomic region contains an operon that contributes to quorum sensing and is involved in persistence, biofilm formation and virulence. BCAM0257-8-9 is found in all sequenced B. cenocepacia ET12 genomes and these results may help explain why infections with strains of the B. cenocepacia ET12 lineage are difficult to treat.
Collapse
Affiliation(s)
- Heleen Van Acker
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Evelien De Canck
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | | | - Andrea Sass
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Dieter Deforce
- Laboratory of Pharmaceutical Biotechnology, Ghent University, Ghent, Belgium
| | - Hans J Nelis
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Tom Coenye
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| |
Collapse
|
25
|
Fazli M, Almblad H, Rybtke ML, Givskov M, Eberl L, Tolker-Nielsen T. Regulation of biofilm formation in Pseudomonas and Burkholderia species. Environ Microbiol 2014; 16:1961-81. [PMID: 24592823 DOI: 10.1111/1462-2920.12448] [Citation(s) in RCA: 190] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 02/12/2014] [Accepted: 02/28/2014] [Indexed: 01/28/2023]
Abstract
In the present review, we describe and compare the molecular mechanisms that are involved in the regulation of biofilm formation by Pseudomonas putida, Pseudomonas fluorescens, Pseudomonas aeruginosa and Burkholderia cenocepacia. Our current knowledge suggests that biofilm formation is regulated by cyclic diguanosine-5'-monophosphate (c-di-GMP), small RNAs (sRNA) and quorum sensing (QS) in all these bacterial species. The systems that employ c-di-GMP as a second messenger regulate the production of exopolysaccharides and surface proteins which function as extracellular matrix components in the biofilms formed by the bacteria. The systems that make use of sRNAs appear to regulate the production of exopolysaccharide biofilm matrix material in all these species. In the pseudomonads, QS regulates the production of extracellular DNA, lectins and biosurfactants which all play a role in biofilm formation. In B.cenocepacia QS regulates the expression of a large surface protein, lectins and extracellular DNA that all function as biofilm matrix components. Although the three regulatory systems all regulate the production of factors used for biofilm formation, the molecular mechanisms involved in transducing the signals into expression of the biofilm matrix components differ between the species. Under the conditions tested, exopolysaccharides appears to be the most important biofilm matrix components for P.aeruginosa, whereas large surface proteins appear to be the most important biofilm matrix components for P.putida, P.fluorescens, and B.cenocepacia.
Collapse
Affiliation(s)
- Mustafa Fazli
- Department of International Health, Immunology, and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark; Department of Genetics and Bioengineering, Faculty of Engineering and Architecture, Yeditepe University, Istanbul, Turkey
| | | | | | | | | | | |
Collapse
|
26
|
Global analysis of the Burkholderia thailandensis quorum sensing-controlled regulon. J Bacteriol 2014; 196:1412-24. [PMID: 24464461 DOI: 10.1128/jb.01405-13] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Burkholderia thailandensis contains three acyl-homoserine lactone quorum sensing circuits and has two additional LuxR homologs. To identify B. thailandensis quorum sensing-controlled genes, we carried out transcriptome sequencing (RNA-seq) analyses of quorum sensing mutants and their parent. The analyses were grounded in the fact that we identified genes coding for factors shown previously to be regulated by quorum sensing among a larger set of quorum-controlled genes. We also found that genes coding for contact-dependent inhibition were induced by quorum sensing and confirmed that specific quorum sensing mutants had a contact-dependent inhibition defect. Additional quorum-controlled genes included those for the production of numerous secondary metabolites, an uncharacterized exopolysaccharide, and a predicted chitin-binding protein. This study provides insights into the roles of the three quorum sensing circuits in the saprophytic lifestyle of B. thailandensis, and it provides a foundation on which to build an understanding of the roles of quorum sensing in the biology of B. thailandensis and the closely related pathogenic Burkholderia pseudomallei and Burkholderia mallei.
Collapse
|
27
|
Suppiger A, Schmid N, Aguilar C, Pessi G, Eberl L. Two quorum sensing systems control biofilm formation and virulence in members of the Burkholderia cepacia complex. Virulence 2014; 4:400-9. [PMID: 23799665 PMCID: PMC3714132 DOI: 10.4161/viru.25338] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Burkholderia cepacia complex (Bcc) consists of 17 closely related species that are problematic opportunistic bacterial pathogens for cystic fibrosis patients and immunocompromised individuals. These bacteria are capable of utilizing two different chemical languages: N-acyl homoserine lactones (AHLs) and cis-2-unsaturated fatty acids. Here we summarize the current knowledge of the underlying molecular architectures of these communication systems, showing how they are interlinked and discussing how they regulate overlapping as well as specific sets of genes. A particular focus is laid on the role of these signaling systems in the formation of biofilms, which are believed to be highly important for chronic infections. We review genes that have been implicated in the sessile lifestyle of this group of bacteria. The new emerging role of the intracellular second messenger cyclic dimeric guanosine monophosphate (c-di-GMP) as a downstream regulator of the fatty acid signaling cascade and as a key factor in biofilm formation is also discussed.
Collapse
Affiliation(s)
- Angela Suppiger
- Department of Microbiology, University of Zürich, Zürich, Switzerland
| | | | | | | | | |
Collapse
|
28
|
The organization of the quorum sensing luxI/R family genes in Burkholderia. Int J Mol Sci 2013; 14:13727-47. [PMID: 23820583 PMCID: PMC3742214 DOI: 10.3390/ijms140713727] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 06/20/2013] [Accepted: 06/24/2013] [Indexed: 12/12/2022] Open
Abstract
Members of the Burkholderia genus of Proteobacteria are capable of living freely in the environment and can also colonize human, animal and plant hosts. Certain members are considered to be clinically important from both medical and veterinary perspectives and furthermore may be important modulators of the rhizosphere. Quorum sensing via N-acyl homoserine lactone signals (AHL QS) is present in almost all Burkholderia species and is thought to play important roles in lifestyle changes such as colonization and niche invasion. Here we present a census of AHL QS genes retrieved from public databases and indicate that the local arrangement (topology) of QS genes, their location within chromosomes and their gene neighborhoods show characteristic patterns that differ between the known Burkholderia clades. In sequence phylogenies, AHL QS genes seem to cluster according to the local gene topology rather than according to the species, which suggests that the basic topology types were present prior to the appearance of current Burkholderia species. The data are available at http://net.icgeb.org/burkholderia/.
Collapse
|
29
|
Subramoni S, Sokol PA. Quorum sensing systems influence Burkholderia cenocepacia virulence. Future Microbiol 2013; 7:1373-87. [PMID: 23231487 DOI: 10.2217/fmb.12.118] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Burkholderia cepacia complex strains communicate using N-acyl homoserine lactones and BDSF-dependent quorum sensing (QS) systems. Burkholderia cenocepacia QS systems include CepIR, CciIR, CepR2 and BDSF. Analysis of CepR, CciIR, CepR2 and RpfF (BDSF synthase) QS regulons revealed that these QS systems both independently regulate and coregulate many target genes, often in an opposing manner. The role of QS and several QS-regulated genes in virulence has been determined using vertebrate, invertebrate and plant infection models. Virulence phenotypes are strain and model dependent, suggesting that different QS-regulated genes are important depending on the strain and type of infection. QS inhibitors in combination with antibiotics can reduce biofilm formation and virulence in infection models.
Collapse
Affiliation(s)
- Sujatha Subramoni
- Department of Microbiology, Immunology & Infectious Diseases, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
| | | |
Collapse
|
30
|
Brackman G, Coenye T. Comment on: Synergistic antibacterial efficacy of early combination treatment with tobramycin and quorum-sensing inhibitors against Pseudomonas aeruginosa in an intraperitoneal foreign-body infection mouse model. J Antimicrob Chemother 2013; 68:2176-7. [PMID: 23615559 DOI: 10.1093/jac/dkt151] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
31
|
Salomon D, Gonzalez H, Updegraff BL, Orth K. Vibrio parahaemolyticus type VI secretion system 1 is activated in marine conditions to target bacteria, and is differentially regulated from system 2. PLoS One 2013; 8:e61086. [PMID: 23613791 PMCID: PMC3628861 DOI: 10.1371/journal.pone.0061086] [Citation(s) in RCA: 152] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 03/06/2013] [Indexed: 12/21/2022] Open
Abstract
Vibrio parahaemolyticus is a marine bacterium that thrives in warm climates. It is a leading cause of gastroenteritis resulting from consumption of contaminated uncooked shellfish. This bacterium harbors two putative type VI secretion systems (T6SS). T6SSs are widespread protein secretion systems found in many Gram-negative bacteria, and are often tightly regulated. For many T6SSs studied to date, the conditions and cues, as well as the regulatory mechanisms that control T6SS activity are unknown. In this study, we characterized the environmental conditions and cues that activate both V. parahaemolyticus T6SSs, and identified regulatory mechanisms that control T6SS gene expression and activity. We monitored the expression and secretion of the signature T6SS secreted proteins Hcp1 and Hcp2, and found that both T6SSs are differentially regulated by quorum sensing and surface sensing. We also showed that T6SS1 and T6SS2 require different temperature and salinity conditions to be active. Interestingly, T6SS1, which is found predominantly in clinical isolates, was most active under warm marine-like conditions. Moreover, we found that T6SS1 has anti-bacterial activity under these conditions. In addition, we identified two transcription regulators in the T6SS1 gene cluster that regulate Hcp1 expression, but are not required for immunity against self-intoxication. Further examination of environmental isolates revealed a correlation between the presence of T6SS1 and virulence of V. parahaemolyticus against other bacteria, and we also showed that different V. parahaemolyticus isolates can outcompete each other. We propose that T6SS1 and T6SS2 play different roles in the V. parahaemolyticus lifestyles, and suggest a role for T6SS1 in enhancing environmental fitness of V. parahaemolyticus in marine environments when competing for a niche in the presence of other bacterial populations.
Collapse
Affiliation(s)
- Dor Salomon
- Department of Molecular Biology, University of Texas Southwestern, Medical Center, Dallas, Texas, United States of America
| | - Herman Gonzalez
- Department of Molecular Biology, University of Texas Southwestern, Medical Center, Dallas, Texas, United States of America
| | - Barrett L. Updegraff
- Department of Molecular Biology, University of Texas Southwestern, Medical Center, Dallas, Texas, United States of America
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern, Medical Center, Dallas, Texas, United States of America
- * E-mail:
| |
Collapse
|
32
|
The unexpected discovery of a novel low-oxygen-activated locus for the anoxic persistence of Burkholderia cenocepacia. ISME JOURNAL 2013; 7:1568-81. [PMID: 23486248 PMCID: PMC3721108 DOI: 10.1038/ismej.2013.36] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 01/25/2013] [Accepted: 01/28/2013] [Indexed: 12/11/2022]
Abstract
Burkholderia cenocepacia is a Gram-negative aerobic bacterium that belongs to a group of opportunistic pathogens displaying diverse environmental and pathogenic lifestyles. B. cenocepacia is known for its ability to cause lung infections in people with cystic fibrosis and it possesses a large 8 Mb multireplicon genome encoding a wide array of pathogenicity and fitness genes. Transcriptomic profiling across nine growth conditions was performed to identify the global gene expression changes made when B. cenocepacia changes niches from an environmental lifestyle to infection. In comparison to exponential growth, the results demonstrated that B. cenocepacia changes expression of over one-quarter of its genome during conditions of growth arrest, stationary phase and surprisingly, under reduced oxygen concentrations (6% instead of 20.9% normal atmospheric conditions). Multiple virulence factors are upregulated during these growth arrest conditions. A unique discovery from the comparative expression analysis was the identification of a distinct, co-regulated 50-gene cluster that was significantly upregulated during growth under low oxygen conditions. This gene cluster was designated the low-oxygen-activated (lxa) locus and encodes six universal stress proteins and proteins predicted to be involved in metabolism, transport, electron transfer and regulation. Deletion of the lxa locus resulted in B. cenocepacia mutants with aerobic growth deficiencies in minimal medium and compromised viability after prolonged incubation in the absence of oxygen. In summary, transcriptomic profiling of B. cenocepacia revealed an unexpected ability of aerobic Burkholderia to persist in the absence of oxygen and identified the novel lxa locus as key determinant of this important ecophysiological trait.
Collapse
|
33
|
Udine C, Brackman G, Bazzini S, Buroni S, Van Acker H, Pasca MR, Riccardi G, Coenye T. Phenotypic and genotypic characterisation of Burkholderia cenocepacia J2315 mutants affected in homoserine lactone and diffusible signal factor-based quorum sensing systems suggests interplay between both types of systems. PLoS One 2013; 8:e55112. [PMID: 23383071 PMCID: PMC3557247 DOI: 10.1371/journal.pone.0055112] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 12/19/2012] [Indexed: 01/30/2023] Open
Abstract
Many putative virulence factors of Burkholderia cenocepacia are controlled by various quorum sensing (QS) circuits. These QS systems either use N-acyl homoserine lactones (AHL) or cis-2-dodecenoic acid ("Burkholderia diffusible signal factor", BDSF) as signalling molecules. Previous work suggested that there is little cross-talk between both types of systems. We constructed mutants in B. cenocepacia strain J2315, in which genes encoding CepI (BCAM1870), CciI (BCAM0239a) and the BDSF synthase (BCAM0581) were inactivated, and also constructed double (ΔcepIΔBCAM0581, ΔcciIΔBCAM0581 and ΔcepIΔcciI) mutants and a triple (ΔcepIΔcciIΔBCAM0581) mutant. Subsequently we investigated phenotypic properties (antibiotic susceptibility, biofilm formation, production of AHL and BDSF, protease activity and virulence in Caenorhabditis elegans) and measured gene expression in these mutants, and this in the presence and absence of added BDSF, AHL or both. The triple mutant was significantly more affected in biofilm formation, antimicrobial susceptibility, virulence in C. elegans, and protease production than either the single or double mutants. The ΔBCAM0581 mutant and the ΔcepIΔBCAM0581 and ΔcciIΔBCAM0581 double mutants produced significantly less AHL compared to the WT strain and the ΔcepI and ΔcciI single mutant, respectively. The expression of cepI and cciI in ΔBCAM0581, was approximately 3-fold and 7-fold (p<0.05) lower than in the WT, respectively. The observed differences in AHL production, expression of cepI and cciI and QS-controlled phenotypes in the ΔBCAM0581 mutant could (at least partially) be restored by addition of BDSF. Our data suggest that, in B. cenocepacia J2315, AHL and BDSF-based QS systems co-regulate the same set of genes, regulate different sets of genes that are involved in the same phenotypes and/or that the BDSF system controls the AHL-based QS system. As the expression of the gene encoding the C6-HSL synthase CciI (and to a lesser extent the C8-HSL synthase CepI) is partially controlled by BDSF, it seems likely that the BDSF QS systems controls AHL production through this system.
Collapse
Affiliation(s)
- Claudia Udine
- Dipartimento di Biologia e Biotecnologie, Università degli Studi di Pavia, Pavia, Italy
| | - Gilles Brackman
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Silvia Bazzini
- Dipartimento di Biologia e Biotecnologie, Università degli Studi di Pavia, Pavia, Italy
| | - Silvia Buroni
- Dipartimento di Biologia e Biotecnologie, Università degli Studi di Pavia, Pavia, Italy
| | - Heleen Van Acker
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Maria Rosalia Pasca
- Dipartimento di Biologia e Biotecnologie, Università degli Studi di Pavia, Pavia, Italy
| | - Giovanna Riccardi
- Dipartimento di Biologia e Biotecnologie, Università degli Studi di Pavia, Pavia, Italy
| | - Tom Coenye
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
- * E-mail:
| |
Collapse
|
34
|
The AHL- and BDSF-dependent quorum sensing systems control specific and overlapping sets of genes in Burkholderia cenocepacia H111. PLoS One 2012. [PMID: 23185499 PMCID: PMC3502180 DOI: 10.1371/journal.pone.0049966] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Quorum sensing in Burkholderia cenocepacia H111 involves two signalling systems that depend on different signal molecules, namely N-acyl homoserine lactones (AHLs) and the diffusible signal factor cis-2-dodecenoic acid (BDSF). Previous studies have shown that AHLs and BDSF control similar phenotypic traits, including biofilm formation, proteolytic activity and pathogenicity. In this study we mapped the BDSF stimulon by RNA-Seq and shotgun proteomics analysis. We demonstrate that a set of the identified BDSF-regulated genes or proteins are also controlled by AHLs, suggesting that the two regulons partially overlap. The detailed analysis of two mutually regulated operons, one encoding three lectins and the other one encoding the large surface protein BapA and its type I secretion machinery, revealed that both AHLs and BDSF are required for full expression, suggesting that the two signalling systems operate in parallel. In accordance with this, we show that both AHLs and BDSF are required for biofilm formation and protease production.
Collapse
|
35
|
Ryan GT, Wei Y, Winans SC. A LuxR-type repressor of Burkholderia cenocepacia inhibits transcription via antiactivation and is inactivated by its cognate acylhomoserine lactone. Mol Microbiol 2012; 87:94-111. [PMID: 23136852 DOI: 10.1111/mmi.12085] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/29/2012] [Indexed: 11/30/2022]
Abstract
Burkholderia cenocepacia is an opportunistic human pathogen that encodes two LuxI-type acylhomoserine lactone (AHL) synthases and three LuxR-type AHL receptors. Of these, cepI and cepR form a cognate synthase/receptor pair, as do cciI and cciR, while cepR2 lacks a genetically linked AHL synthase gene. Another group showed that a cepR2 mutant overexpressed a cluster of linked genes that appear to direct the production of a secondary metabolite. We found that these same genes were upregulated by octanoylhomoserine lactone (OHL), which is synthesized by CepI. These data suggest that several cepR2-linked promoters are repressed by CepR2 and that CepR2 is antagonized by OHL. Fusions of two divergent promoters to lacZ were used to confirm these hypotheses, and promoter resections and DNase I footprinting assays revealed a single CepR2 binding site between the two promoters. This binding site lies well upstream of both promoters, suggesting an unusual mode of repression. Adjacent to the cepR2 gene is a gene that we designate cepS, which encodes an AraC-type transcription factor. CepS is essential for expression of both promoters, regardless of the CepR2 status or OHL concentration. CepS therefore acts downstream of CepR2, and CepR2 appears to function as a CepS antiactivator.
Collapse
Affiliation(s)
- Gina T Ryan
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | | | | |
Collapse
|
36
|
Inhülsen S, Aguilar C, Schmid N, Suppiger A, Riedel K, Eberl L. Identification of functions linking quorum sensing with biofilm formation in Burkholderia cenocepacia H111. Microbiologyopen 2012; 1:225-42. [PMID: 22950027 PMCID: PMC3426421 DOI: 10.1002/mbo3.24] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Revised: 03/29/2012] [Accepted: 04/03/2012] [Indexed: 01/08/2023] Open
Abstract
Burkholderia cenocepacia has emerged as an important pathogen for patients suffering from cystic fibrosis (CF). Previous work has shown that this organism employs the CepIR quorum-sensing (QS) system to control the expression of virulence factors as well as the formation of biofilms. To date, however, very little is known about the QS-regulated virulence factors and virtually nothing about the factors that link QS and biofilm formation. Here, we have employed a combined transcriptomic and proteomic approach to precisely define the QS regulon in our model strain B. cenocepacia H111, a CF isolate. Among the identified CepR-activated loci, three were analyzed in better detail for their roles in biofilm development: (i) a gene cluster coding for the BclACB lectins, (ii) the large surface protein BapA, and (iii) a type I pilus. The analysis of defined mutants revealed that BapA plays a major role in biofilm formation on abiotic surfaces while inactivation of the type I pilus showed little effect both in a static microtitre dish-based biofilm assay and in flow-through cells. Inactivation of the bclACB lectin genes resulted in biofilms containing hollow microcolonies, suggesting that the lectins are important for biofilm structural development.
Collapse
Affiliation(s)
- Silja Inhülsen
- Department of Microbiology, Institute of Plant Biology, University of ZurichZollikerstrasse, 107, 8008 Zurich, Switzerland
| | - Claudio Aguilar
- Department of Microbiology, Institute of Plant Biology, University of ZurichZollikerstrasse, 107, 8008 Zurich, Switzerland
| | - Nadine Schmid
- Department of Microbiology, Institute of Plant Biology, University of ZurichZollikerstrasse, 107, 8008 Zurich, Switzerland
| | - Angela Suppiger
- Department of Microbiology, Institute of Plant Biology, University of ZurichZollikerstrasse, 107, 8008 Zurich, Switzerland
| | - Kathrin Riedel
- Institute of Microbiology, Ernst-Moritz-Arndt University of GreifswaldFriedrich-Ludwig-Jahn-Strasse 15, D-17487, Greifswald,, Germany
| | - Leo Eberl
- Department of Microbiology, Institute of Plant Biology, University of ZurichZollikerstrasse, 107, 8008 Zurich, Switzerland
| |
Collapse
|
37
|
Aubert DF, O'Grady EP, Hamad MA, Sokol PA, Valvano MA. The Burkholderia cenocepacia sensor kinase hybrid AtsR is a global regulator modulating quorum-sensing signalling. Environ Microbiol 2012; 15:372-85. [PMID: 22830644 DOI: 10.1111/j.1462-2920.2012.02828.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Burkholderia cenocepacia is commonly found in the environment and also as an important opportunistic pathogen infecting patients with cystic fibrosis. Successful infection by this bacterium requires coordinated expression of virulence factors, which is achieved through different quorum sensing (QS) regulatory systems. Biofilm formation and Type 6 secretion system (T6SS) expression in B. cenocepacia K56-2 are positively regulated by QS and negatively regulated by the sensor kinase hybrid AtsR. This study reveals that in addition to affecting biofilm and T6SS activity, the deletion of atsR in B. cenocepacia leads to overproduction of other QS-regulated virulence determinants including proteases and swarming motility. Expression of the QS genes, cepIR and cciIR, was upregulated in the ΔatsR mutant and resulted in early and increased N-acylhomoserine lactone (AHL) production, suggesting that AtsR plays a role in controlling the timing and fine-tuning of virulence gene expression by modulating QS signalling. Furthermore, a ΔatsRΔcepIΔcciI mutant could partially upregulate the same virulence determinants indicating that AtsR also modulates the expression of virulence genes by a second mechanism, independently of any AHL production. Together, our results strongly suggest that AtsR is a global virulence regulator in B. cenocepacia.
Collapse
Affiliation(s)
- Daniel F Aubert
- Centre for Human Immunology, Department of Microbiology, University of Western Ontario, London, Ontario, Canada
| | | | | | | | | |
Collapse
|
38
|
O'Grady EP, Viteri DF, Sokol PA. A unique regulator contributes to quorum sensing and virulence in Burkholderia cenocepacia. PLoS One 2012; 7:e37611. [PMID: 22624054 PMCID: PMC3356288 DOI: 10.1371/journal.pone.0037611] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 04/23/2012] [Indexed: 01/08/2023] Open
Abstract
Burkholderia cenocepacia causes chronic and life-threatening respiratory infections in immunocompromized people. The B. cenocepacia N-acyl-homoserine lactone (AHL)-dependent quorum sensing system relies on the production of AHLs by the synthases CepI and CciI while CepR, CciR and CepR2 control expression of many genes important for pathogenesis. Downstream from, and co-transcribed with cepI, lies BCAM1871 encoding a hypothetical protein that was uncharacterized prior to this study. Orthologs of B. cenocepacia BCAM1871 are uniquely found in Burkholderia spp and are conserved in their genomic locations in pathogenic Burkholderia. We observed significant effects on AHL activity upon mutation or overexpression of BCAM1871, although these effects were more subtle than those observed for CepI indicating BCAM1871 acts as an enhancer of AHL activity. Transcription of cepI, cepR and cciIR was significantly reduced in the BCAM1871 mutant. Swimming and swarming motilities as well as transcription of fliC, encoding flagellin, were significantly reduced in the BCAM1871 mutant. Protease activity and transcription of zmpA and zmpB, encoding extracellular zinc metalloproteases, were undetectable in the BCAM1871 mutant indicating a more significant effect of mutating BCAM1871 than cepI. Exogenous addition of OHL restored cepI, cepR and fliC transcription but had no effect on motility, protease activity or zmpA or zmpB transcription suggesting AHL-independent effects. The BCAM1871 mutant exhibited significantly reduced virulence in rat chronic respiratory and nematode infection models. Gene expression and phenotypic assays as well as vertebrate and invertebrate infection models showed that BCAM1871 significantly contributes to pathogenesis in B. cenocepacia.
Collapse
Affiliation(s)
| | | | - Pamela A. Sokol
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
- * E-mail:
| |
Collapse
|
39
|
Tolman JS, Valvano MA. Global changes in gene expression by the opportunistic pathogen Burkholderia cenocepacia in response to internalization by murine macrophages. BMC Genomics 2012; 13:63. [PMID: 22321740 PMCID: PMC3296584 DOI: 10.1186/1471-2164-13-63] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 02/09/2012] [Indexed: 12/18/2022] Open
Abstract
Background Burkholderia cenocepacia is an opportunistic pathogen causing life-threatening infections in patients with cystic fibrosis. The bacterium survives within macrophages by interfering with endocytic trafficking and delaying the maturation of the B. cenocepacia-containing phagosome. We hypothesize that B. cenocepacia undergoes changes in gene expression after internalization by macrophages, inducing genes involved in intracellular survival and host adaptation. Results We examined gene expression by intracellular B. cenocepacia using selective capture of transcribed sequences (SCOTS) combined with microarray analysis. We identified 767 genes with significantly different levels of expression by intracellular bacteria, of which 330 showed increased expression and 437 showed decreased expression. Affected genes represented all aspects of cellular life including information storage and processing, cellular processes and signaling, and metabolism. In general, intracellular gene expression demonstrated a pattern of environmental sensing, bacterial response, and metabolic adaptation to the phagosomal environment. Deletion of various SCOTS-identified genes affected bacterial entry into macrophages and intracellular replication. We also show that intracellular B. cenocepacia is cytotoxic towards the macrophage host, and capable of spread to neighboring cells, a role dependent on SCOTS-identified genes. In particular, genes involved in bacterial motility, cobalamin biosynthesis, the type VI secretion system, and membrane modification contributed greatly to macrophage entry and subsequent intracellular behavior of B. cenocepacia. Conclusions B. cenocepacia enters macrophages, adapts to the phagosomal environment, replicates within a modified phagosome, and exhibits cytotoxicity towards the host cells. The analysis of the transcriptomic response of intracellular B. cenocepacia reveals that metabolic adaptation to a new niche plays a major role in the survival of B. cenocepacia in macrophages. This adaptive response does not require the expression of any specific virulence-associated factor, which is consistent with the opportunistic nature of this microorganism. Further investigation into the remaining SCOTS-identified genes will provide a more complete picture of the adaptive response of B. cenocepacia to the host cell environment.
Collapse
Affiliation(s)
- Jennifer S Tolman
- Infectious Diseases Research Group, Department of Microbiology & Immunology, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | | |
Collapse
|
40
|
Semler DD, Lynch KH, Dennis JJ. The promise of bacteriophage therapy for Burkholderia cepacia complex respiratory infections. Front Cell Infect Microbiol 2012; 1:27. [PMID: 22919592 PMCID: PMC3417384 DOI: 10.3389/fcimb.2011.00027] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Accepted: 12/31/2011] [Indexed: 11/13/2022] Open
Abstract
In recent times, increased attention has been given to evaluating the efficacy of phage therapy, especially in scenarios where the bacterial infectious agent of interest is highly antibiotic resistant. In this regard, phage therapy is especially applicable to infections caused by the Burkholderia cepacia complex (BCC) since members of the BCC are antibiotic pan-resistant. Current studies in BCC phage therapy are unique from many other avenues of phage therapy research in that the investigation is not only comprised of phage isolation, in vitro phage characterization and assessment of in vivo infection model efficacy, but also adapting aerosol drug delivery techniques to aerosol phage formulation delivery and storage.
Collapse
Affiliation(s)
- Diana D. Semler
- Department of Biological Sciences, Centennial Centre for Interdisciplinary Science, University of AlbertaEdmonton, AB, Canada
| | - Karlene H. Lynch
- Department of Biological Sciences, Centennial Centre for Interdisciplinary Science, University of AlbertaEdmonton, AB, Canada
| | - Jonathan J. Dennis
- Department of Biological Sciences, Centennial Centre for Interdisciplinary Science, University of AlbertaEdmonton, AB, Canada
| |
Collapse
|
41
|
Hauberg-Lotte L, Klingenberg H, Scharf C, Böhm M, Plessl J, Friedrich F, Völker U, Becker A, Reinhold-Hurek B. Environmental factors affecting the expression of pilAB as well as the proteome and transcriptome of the grass endophyte Azoarcus sp. strain BH72. PLoS One 2012; 7:e30421. [PMID: 22276194 PMCID: PMC3262810 DOI: 10.1371/journal.pone.0030421] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 12/15/2011] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Bacterial communication is involved in regulation of cellular mechanisms such as metabolic processes, microbe-host interactions or biofilm formation. In the nitrogen-fixing model endophyte of grasses Azoarcus sp. strain BH72, known cell-cell signaling systems have not been identified; however, the pilA gene encoding the structural protein of type IV pili that are essential for plant colonization appears to be regulated in a population density-dependent manner. METHODOLOGY/PRINCIPAL FINDINGS Our data suggest that pilAB expression is affected by population density, independent of autoinducers typical for gram-negative bacteria, likely depending on unknown secreted molecule(s) that can be produced by different bacterial species. We used transcriptomic and proteomic approaches to identify target genes and proteins differentially regulated in conditioned supernatants in comparison to standard growth conditions. Around 8% of the 3992 protein-coding genes of Azoarcus sp. and 18% of the detected proteins were differentially regulated. Regulatory proteins and transcription factors among the regulated proteins indicated a complex hierarchy. Differentially regulated genes and proteins were involved in processes such as type IV pili formation and regulation, metal and nutrient transport, energy metabolism, and unknown functions mediated by hypothetical proteins. Four of the newly discovered target genes were further analyzed and in general they showed regulation patterns similar to pilAB. The expression of one of them was shown to be induced in plant roots. CONCLUSION/SIGNIFICANCE This study is the first global approach to initiate characterization of cell density-dependent gene regulation mediated by soluble molecule(s) in the model endophyte Azoarcus sp. strain BH72. Our data suggest that the putative signaling molecule(s) are also produced by other Proteobacteria and might thus be used for interspecies communication. This study provides the foundation for the development of robust reporter systems for Azoarcus sp. to analyze mechanisms and molecules involved in the population-dependent gene expression in this endophyte in future.
Collapse
Affiliation(s)
- Lena Hauberg-Lotte
- University Bremen, Molecular Plant Microbiology, Center for Biomolecular Interactions Bremen, Bremen, Germany
| | - Hannah Klingenberg
- University Bremen, Molecular Plant Microbiology, Center for Biomolecular Interactions Bremen, Bremen, Germany
| | - Christian Scharf
- Ernst-Moritz-Arndt-University Greifswald, Interfaculty Institute of Genetics and Functional Genomics, Greifswald, Germany
- University of Medicine Greifswald, Department of Otorhinolaryngology, Greifswald, Germany
| | - Melanie Böhm
- University Bremen, Molecular Plant Microbiology, Center for Biomolecular Interactions Bremen, Bremen, Germany
| | - Jörg Plessl
- University Bremen, Molecular Plant Microbiology, Center for Biomolecular Interactions Bremen, Bremen, Germany
| | - Frauke Friedrich
- University Bremen, Molecular Plant Microbiology, Center for Biomolecular Interactions Bremen, Bremen, Germany
| | - Uwe Völker
- Ernst-Moritz-Arndt-University Greifswald, Interfaculty Institute of Genetics and Functional Genomics, Greifswald, Germany
| | - Anke Becker
- Institute of Biology III, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Barbara Reinhold-Hurek
- University Bremen, Molecular Plant Microbiology, Center for Biomolecular Interactions Bremen, Bremen, Germany
| |
Collapse
|
42
|
Genomic expression analysis reveals strategies of Burkholderia cenocepacia to adapt to cystic fibrosis patients' airways and antimicrobial therapy. PLoS One 2011; 6:e28831. [PMID: 22216120 PMCID: PMC3244429 DOI: 10.1371/journal.pone.0028831] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 11/15/2011] [Indexed: 12/20/2022] Open
Abstract
Pulmonary colonization of cystic fibrosis (CF) patients with Burkholderia cenocepacia or other bacteria of the Burkholderia cepacia complex (Bcc) is associated with worse prognosis and increased risk of death. During colonization, the bacteria may evolve under the stressing selection pressures exerted in the CF lung, in particular, those resulting from challenges of the host immune defenses, antimicrobial therapy, nutrient availability and oxygen limitation. Understanding the adaptive mechanisms that promote successful colonization and long-term survival of B. cenocepacia in the CF lung is essential for an improved therapeutic outcome of chronic infections. To get mechanistic insights into these adaptive strategies a transcriptomic analysis, based on DNA microarrays, was explored in this study. The genomic expression levels in two clonal variants isolated during long-term colonization of a CF patient who died from the cepacia syndrome were compared. One of the isolates examined, IST439, is the first B. cenocepacia isolate retrieved from the patient and the other isolate, IST4113, was obtained three years later and is more resistant to different classes of antimicrobials. Approximately 1000 genes were found to be differently expressed in the two clonal variants reflecting a marked reprogramming of genomic expression. The up-regulated genes in IST4113 include those involved in translation, iron uptake (in particular, in ornibactin biosynthesis), efflux of drugs and in adhesion to epithelial lung tissue and to mucin. Alterations related with adaptation to the nutritional environment of the CF lung and to an oxygen-limited environment are also suggested to be a key feature of transcriptional reprogramming occurring during long-term colonization, antibiotic therapy and the progression of the disease.
Collapse
|
43
|
Agnoli K, Schwager S, Uehlinger S, Vergunst A, Viteri DF, Nguyen DT, Sokol PA, Carlier A, Eberl L. Exposing the third chromosome of Burkholderia cepacia complex strains as a virulence plasmid. Mol Microbiol 2011; 83:362-78. [PMID: 22171913 DOI: 10.1111/j.1365-2958.2011.07937.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Burkholderia cepacia complex (Bcc) consists of 17 closely related species of opportunistic bacterial pathogens, which are particularly problematic for cystic fibrosis patients and immunocompromised individuals. Bcc genomes consist of multiple replicons, and each strain sequenced to date has three chromosomes. In addition to genes thought to be essential for survival, each chromosome carries at least one rRNA operon. We isolated three mutants during a transposon mutagenesis screen that were non-pathogenic in a Caenorhabditis elegans infection model. It was demonstrated that these mutants had lost chromosome 3 (c3), and that the observed attenuation of virulence was a consequence of this. We constructed a c3 mini-replicon and used it to cure c3 from strains of several Bcc species by plasmid incompatibility, resulting in nine c3-null strains covering seven Bcc species. Phenotypic characterization of c3-null mutants revealed that they were attenuated in virulence in multiple infection hosts (rat, zebrafish, C. elegans, Galleria mellonella and Drosophila melanogaster), that they exhibited greatly diminished antifungal activity, and that c3 was required for d-xylose, fatty acid and pyrimidine utilization, as well as for exopolysaccharide production and proteolytic activity in some strains. In conclusion, we show that c3 is not an essential chromosomal element, rather a large plasmid that encodes virulence, secondary metabolism and other accessory functions in Bcc bacteria.
Collapse
Affiliation(s)
- K Agnoli
- Department of Microbiology, Institute of Plant Biology, University of Zürich, Zollikerstrasse 107. CH-8008 Zürich, Switzerland
| | | | | | | | | | | | | | | | | |
Collapse
|
44
|
O'Grady EP, Sokol PA. Burkholderia cenocepacia differential gene expression during host-pathogen interactions and adaptation to the host environment. Front Cell Infect Microbiol 2011; 1:15. [PMID: 22919581 PMCID: PMC3417382 DOI: 10.3389/fcimb.2011.00015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 11/20/2011] [Indexed: 01/08/2023] Open
Abstract
Members of the Burkholderia cepacia complex (Bcc) are important in medical, biotechnological, and agricultural disciplines. These bacteria naturally occur in soil and water environments and have adapted to survive in association with plants and animals including humans. All Bcc species are opportunistic pathogens including Burkholderia cenocepacia that causes infections in cystic fibrosis and chronic granulomatous disease patients. The adaptation of B. cenocepacia to the host environment was assessed in a rat chronic respiratory infection model and compared to that of high cell-density in vitro grown cultures using transcriptomics. The distribution of genes differentially expressed on chromosomes 1, 2, and 3 was relatively proportional to the size of each genomic element, whereas the proportion of plasmid-encoded genes differentially expressed was much higher relative to its size and most genes were induced in vivo. The majority of genes encoding known virulence factors, components of types II and III secretion systems and chromosome 2-encoded type IV secretion system were similarly expressed between in vitro and in vivo environments. Lower expression in vivo was detected for genes encoding N-acyl-homoserine lactone synthase CepI, orphan LuxR homolog CepR2, zinc metalloproteases ZmpA and ZmpB, LysR-type transcriptional regulator ShvR, nematocidal protein AidA, and genes associated with flagellar motility, Flp type pilus formation, and type VI secretion. Plasmid-encoded type IV secretion genes were markedly induced in vivo. Additional genes induced in vivo included genes predicted to be involved in osmotic stress adaptation or intracellular survival, metal ion, and nutrient transport, as well as those encoding outer membrane proteins. Genes identified in this study are potentially important for virulence during host–pathogen interactions and may be associated with survival and adaptation to the host environment during chronic lung infections.
Collapse
Affiliation(s)
- Eoin P O'Grady
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, AB, Canada
| | | |
Collapse
|
45
|
Abstract
Many bacteria use 'quorum sensing' (QS) as a mechanism to regulate gene induction in a population-dependent manner. In its simplest sense this involves the accumulation of a signaling metabolite during growth; the binding of this metabolite to a regulator or multiple regulators activates induction or repression of gene expression. However QS regulation is seldom this simple, because other inputs are usually involved. In this review we have focussed on how those other inputs influence QS regulation and as implied by the title, this often occurs by environmental or physiological effects regulating the expression or activity of the QS regulators. The rationale of this review is to briefly introduce the main QS signals used in Gram-negative bacteria and then introduce one of the earliest understood mechanisms of regulation of the regulator, namely the plant-mediated control of expression of the TraR QS regulator in Agrobacterium tumefaciens. We then describe how in several species, multiple QS regulatory systems can act as integrated hierarchical regulatory networks and usually this involves the regulation of QS regulators. Such networks can be influenced by many different physiological and environmental inputs and we describe diverse examples of these. In the final section, we describe different examples of how eukaryotes can influence QS regulation in Gram-negative bacteria.
Collapse
Affiliation(s)
- Marijke Frederix
- Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | | |
Collapse
|
46
|
Molecular approaches to pathogenesis study of Burkholderia cenocepacia, an important cystic fibrosis opportunistic bacterium. Appl Microbiol Biotechnol 2011; 92:887-95. [PMID: 21997606 DOI: 10.1007/s00253-011-3616-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 09/08/2011] [Accepted: 09/28/2011] [Indexed: 10/15/2022]
Abstract
Burkholderia cenocepacia is a Gram-negative opportunistic pathogen belonging to the Burkholderia cepacia complex (Bcc). It is spread in a wide range of ecological niches, and in cystic fibrosis patients, it is responsible for serious infections. Its eradication is very difficult due to the high level of intrinsic resistance to clinically relevant antibiotics. One of the main resistance mechanisms in clinical isolates is represented by efflux systems that are able to extrude a variety of molecules, such as antibiotics, out of the cell. Resistance-Nodulation-Cell Division (RND) efflux pumps are known to be mediators of multidrug resistance in Gram-negative bacteria. Since now, the significance of the RND efflux systems in B. cenocepacia has been partially determined. However, the analysis of the completely sequenced genome of B. cenocepacia J2315 allowed the identification of 16 operons coding for these transporters. We focused our attention on the role of these pumps through the construction of several deletion mutants. Since manipulating B. cenocepacia J2315 genome is difficult, we used a peculiar inactivation system, which enables different deletions in the same strain. The characterization of our mutants through transcriptome and phenotype microarray analysis suggested that RND efflux pumps can be involved not only in drug resistance but also in pathways important for the pathogenesis of this microorganism. The aim of this review is an updated overview on host-pathogen interactions and drug resistance, particularly focused on RND-mediated efflux mechanisms, highlighting the importance of molecular techniques in the study of B. cenocepacia.
Collapse
|
47
|
Spontaneous and evolutionary changes in the antibiotic resistance of Burkholderia cenocepacia observed by global gene expression analysis. BMC Genomics 2011; 12:373. [PMID: 21781329 PMCID: PMC3155924 DOI: 10.1186/1471-2164-12-373] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 07/22/2011] [Indexed: 11/29/2022] Open
Abstract
Background Burkholderia cenocepacia is a member of the Burkholderia cepacia complex group of bacteria that cause infections in individuals with cystic fibrosis. B. cenocepacia isolate J2315 has been genome sequenced and is representative of a virulent, epidemic CF strain (ET12). Its genome encodes multiple antimicrobial resistance pathways and it is not known which of these is important for intrinsic or spontaneous resistance. To map these pathways, transcriptomic analysis was performed on: (i) strain J2315 exposed to sub-inhibitory concentrations of antibiotics and the antibiotic potentiator chlorpromazine, and (ii) on spontaneous mutants derived from J2315 and with increased resistance to the antibiotics amikacin, meropenem and trimethoprim-sulfamethoxazole. Two pan-resistant ET12 outbreak isolates recovered two decades after J2315 were also compared to identify naturally evolved gene expression changes. Results Spontaneous resistance in B. cenocepacia involved more gene expression changes and different subsets of genes than those provoked by exposure to sub inhibitory concentrations of each antibiotic. The phenotype and altered gene expression in the resistant mutants was also stable irrespective of the presence of the priming antibiotic. Both known and novel genes involved in efflux, antibiotic degradation/modification, membrane function, regulation and unknown functions were mapped. A novel role for the phenylacetic acid (PA) degradation pathway genes was identified in relation to spontaneous resistance to meropenem and glucose was found to repress their expression. Subsequently, 20 mM glucose was found to produce greater that 2-fold reductions in the MIC of multiple antibiotics against B. cenocepacia J2315. Mutation of an RND multidrug efflux pump locus (BCAM0925-27) and squalene-hopene cyclase gene (BCAS0167), both upregulated after chlorpromazine exposure, confirmed their role in resistance. The recently isolated outbreak isolates had altered the expression of multiple genes which mirrored changes seen in the antibiotic resistant mutants, corroborating the strategy used to model resistance. Mutation of an ABC transporter gene (BCAS0081) upregulated in both outbreak strains, confirmed its role in B. cenocepacia resistance. Conclusions Global mapping of the genetic pathways which mediate antibiotic resistance in B. cenocepacia has revealed that they are multifactorial, identified potential therapeutic targets and also demonstrated that putative catabolite repression of genes by glucose can improve antibiotic efficacy.
Collapse
|
48
|
Burkholderia cenocepacia ShvR-regulated genes that influence colony morphology, biofilm formation, and virulence. Infect Immun 2011; 79:2984-97. [PMID: 21690240 DOI: 10.1128/iai.00170-11] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Burkholderia cenocepacia is an opportunistic pathogen that primarily infects cystic fibrosis (CF) patients. Previously, we reported that ShvR, a LysR regulator, influences colony morphology, virulence, and biofilm formation and regulates the expression of an adjacent 24-kb genomic region encoding 24 genes. In this study, we report the functional characterization of selected genes in this region. A Tn5 mutant with shiny colony morphology was identified with a polar mutation in BCAS0208, predicted to encode an acyl-coenzyme A dehydrogenase. Mutagenesis of BCAS0208 and complementation analyses revealed that BCAS0208 is required for rough colony morphology, biofilm formation, and virulence on alfalfa seedlings. It was not possible to complement with BCAS0208 containing a mutation in the catalytic site. BCAS0201, encoding a putative flavin adenine dinucleotide (FAD)-dependent oxidoreductase, and BCAS0207, encoding a putative citrate synthase, do not influence colony morphology but are required for optimum levels of biofilm formation and virulence. Both BCAS0208 and BCAS0201 contribute to pellicle formation, although individual mutations in each of these genes had no appreciable effect on pellicle formation. A mutant with a polar insertion in BCAS0208 was significantly less virulent in a rat model of chronic lung infection as well as in the alfalfa model. Genes in this region were shown to influence utilization of branched-chain fatty acids, tricarboxylic acid cycle substrates, l-arabinose, and branched-chain amino acids. Together, our data show that the ShvR-regulated genes BCAS0208 to BCAS0201 are required for the rough colony morphotype, biofilm and pellicle formation, and virulence in B. cenocepacia.
Collapse
|
49
|
Hypervirulent Chlamydia trachomatis clinical strain is a recombinant between lymphogranuloma venereum (L(2)) and D lineages. mBio 2011; 2:e00045-11. [PMID: 21540364 PMCID: PMC3088116 DOI: 10.1128/mbio.00045-11] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Chlamydia trachomatis is an obligate intracellular bacterium that causes a diversity of severe and debilitating diseases worldwide. Sporadic and ongoing outbreaks of lymphogranuloma venereum (LGV) strains among men who have sex with men (MSM) support the need for research on virulence factors associated with these organisms. Previous analyses have been limited to single genes or genomes of laboratory-adapted reference strain L2/434 and outbreak strain L2b/UCH-1/proctitis. We characterized an unusual LGV strain, termed L2c, isolated from an MSM with severe hemorrhagic proctitis. L2c developed nonfusing, grape-like inclusions and a cytotoxic phenotype in culture, unlike the LGV strains described to date. Deep genome sequencing revealed that L2c was a recombinant of L2 and D strains with conserved clustered regions of genetic exchange, including a 78-kb region and a partial, yet functional, toxin gene that was lost with prolonged culture. Indels (insertions/deletions) were discovered in an ftsK gene promoter and in the tarp and hctB genes, which encode key proteins involved in replication, inclusion formation, and histone H1-like protein activity, respectively. Analyses suggest that these indels affect gene and/or protein function, supporting the in vitro and disease phenotypes. While recombination has been known to occur for C. trachomatis based on gene sequence analyses, we provide the first whole-genome evidence for recombination between a virulent, invasive LGV strain and a noninvasive common urogenital strain. Given the lack of a genetic system for producing stable C. trachomatis mutants, identifying naturally occurring recombinants can clarify gene function and provide opportunities for discovering avenues for genomic manipulation. Lymphogranuloma venereum (LGV) is a prevalent and debilitating sexually transmitted disease in developing countries, although there are significant ongoing outbreaks in Australia, Europe, and the United States among men who have sex with men (MSM). Relatively little is known about LGV virulence factors, and only two LGV genomes have been sequenced to date. We isolated an LGV strain from an MSM with severe hemorrhagic proctitis that was morphologically unique in tissue culture compared with other LGV strains. Bioinformatic and statistical analyses identified the strain as a recombinant of L2 and D strains with highly conserved clustered regions of genetic exchange. The unique culture morphology and, more importantly, disease phenotype could be traced to the genes involved in recombination. The findings have implications for bacterial species evolution and, in the case of ongoing LGV outbreaks, suggest that recombination is a mechanism for strain emergence that results in significant disease pathology.
Collapse
|
50
|
Wei Y, Ryan GT, Flores-Mireles AL, Costa ED, Schneider DJ, Winans SC. Saturation mutagenesis of a CepR binding site as a means to identify new quorum-regulated promoters in Burkholderia cenocepacia. Mol Microbiol 2011; 79:616-32. [PMID: 21255107 DOI: 10.1111/j.1365-2958.2010.07469.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Burkholderia cenocepacia is an opportunistic pathogen of humans that encodes two genes that resemble the acylhomoserine lactone synthase gene luxI of Vibrio fischeri and three genes that resemble the acylhomoserine lactone receptor gene luxR. Of these, CepI synthesizes octanoylhomoserine lactone (OHL), while CepR is an OHL-dependent transcription factor. In the current study we developed a strategy to identify genes that are directly regulated by CepR. We systematically altered a CepR binding site (cep box) upstream of a target promoter to identify nucleotides that are essential for CepR activity in vivo and for CepR binding in vitro. We constructed 34 self-complementary oligonucleotides containing altered cep boxes, and measured binding affinity for each. These experiments allowed us to identify a consensus CepR binding site. Several hundred similar sequences were identified, some of which were adjacent to probable promoters. Several such promoters were fused to a reporter gene with and without intact cep boxes. This allowed us to identify four new regulated promoters that were induced by OHL, and that required a cep box for induction. CepR-dependent, OHL-dependent expression of all four promoters was reconstituted in Escherichia coli. Purified CepR bound to each of these sites in electrophoretic mobility shift assays.
Collapse
Affiliation(s)
- Yuping Wei
- Departments of Microbiology Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, USA
| | | | | | | | | | | |
Collapse
|