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Challacombe JF, Stubben CJ, Klimko CP, Welkos SL, Kern SJ, Bozue JA, Worsham PL, Cote CK, Wolfe DN. Interrogation of the Burkholderia pseudomallei genome to address differential virulence among isolates. PLoS One 2014; 9:e115951. [PMID: 25536074 PMCID: PMC4275268 DOI: 10.1371/journal.pone.0115951] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 12/01/2014] [Indexed: 11/18/2022] Open
Abstract
Infection by the Gram-negative pathogen Burkholderia pseudomallei results in the disease melioidosis, acquired from the environment in parts of southeast Asia and northern Australia. Clinical symptoms of melioidosis range from acute (fever, pneumonia, septicemia, and localized infection) to chronic (abscesses in various organs and tissues, most commonly occurring in the lungs, liver, spleen, kidney, prostate and skeletal muscle), and persistent infections in humans are difficult to cure. Understanding the basic biology and genomics of B. pseudomallei is imperative for the development of new vaccines and therapeutic interventions. This formidable task is becoming more tractable due to the increasing number of B. pseudomallei genomes that are being sequenced and compared. Here, we compared three B. pseudomallei genomes, from strains MSHR668, K96243 and 1106a, to identify features that might explain why MSHR668 is more virulent than K96243 and 1106a in a mouse model of B. pseudomallei infection. Our analyses focused on metabolic, virulence and regulatory genes that were present in MSHR668 but absent from both K96243 and 1106a. We also noted features present in K96243 and 1106a but absent from MSHR668, and identified genomic differences that may contribute to variations in virulence noted among the three B. pseudomallei isolates. While this work contributes to our understanding of B. pseudomallei genomics, more detailed experiments are necessary to characterize the relevance of specific genomic features to B. pseudomallei metabolism and virulence. Functional analyses of metabolic networks, virulence and regulation shows promise for examining the effects of B. pseudomallei on host cell metabolism and will lay a foundation for future prediction of the virulence of emerging strains. Continued emphasis in this area will be critical for protection against melioidosis, as a better understanding of what constitutes a fully virulent Burkholderia isolate may provide for better diagnostic and medical countermeasure strategies.
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Affiliation(s)
- Jean F. Challacombe
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, United States of America
- * E-mail:
| | - Chris J. Stubben
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, United States of America
| | - Christopher P. Klimko
- US Army Medical Research Institute of Infectious Diseases, Bacteriology Division, Fort Detrick, MD, United States of America
| | - Susan L. Welkos
- US Army Medical Research Institute of Infectious Diseases, Bacteriology Division, Fort Detrick, MD, United States of America
| | - Steven J. Kern
- US Army Medical Research Institute of Infectious Diseases, Biostatistics Division, Fort Detrick, MD, United States of America
| | - Joel A. Bozue
- US Army Medical Research Institute of Infectious Diseases, Bacteriology Division, Fort Detrick, MD, United States of America
| | - Patricia L. Worsham
- US Army Medical Research Institute of Infectious Diseases, Bacteriology Division, Fort Detrick, MD, United States of America
| | - Christopher K. Cote
- US Army Medical Research Institute of Infectious Diseases, Bacteriology Division, Fort Detrick, MD, United States of America
| | - Daniel N. Wolfe
- Defense Threat Reduction Agency, Chemical and Biological Technologies Department, Fort Belvoir, VA, United States of America
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Musson JA, Reynolds CJ, Rinchai D, Nithichanon A, Khaenam P, Favry E, Spink N, Chu KKY, De Soyza A, Bancroft GJ, Lertmemongkolchai G, Maillere B, Boyton RJ, Altmann DM, Robinson JH. CD4+ T cell epitopes of FliC conserved between strains of Burkholderia: implications for vaccines against melioidosis and cepacia complex in cystic fibrosis. THE JOURNAL OF IMMUNOLOGY 2014; 193:6041-9. [PMID: 25392525 DOI: 10.4049/jimmunol.1402273] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Burkholderia pseudomallei is the causative agent of melioidosis characterized by pneumonia and fatal septicemia and prevalent in Southeast Asia. Related Burkholderia species are strong risk factors of mortality in cystic fibrosis (CF). The B. pseudomallei flagellar protein FliC is strongly seroreactive and vaccination protects challenged mice. We assessed B. pseudomallei FliC peptide binding affinity to multiple HLA class II alleles and then assessed CD4 T cell immunity in HLA class II transgenic mice and in seropositive individuals in Thailand. T cell hybridomas were generated to investigate cross-reactivity between B. pseudomallei and the related Burkholderia species associated with Cepacia Complex CF. B. pseudomallei FliC contained several peptide sequences with ability to bind multiple HLA class II alleles. Several peptides were shown to encompass strong CD4 T cell epitopes in B. pseudomallei-exposed individuals and in HLA transgenic mice. In particular, the p38 epitope is robustly recognized by CD4 T cells of seropositive donors across diverse HLA haplotypes. T cell hybridomas against an immunogenic B. pseudomallei FliC epitope also cross-reacted with orthologous FliC sequences from Burkholderia multivorans and Burkholderia cenocepacia, important pathogens in CF. Epitopes within FliC were accessible for processing and presentation from live or heat-killed bacteria, demonstrating that flagellin enters the HLA class II Ag presentation pathway during infection of macrophages with B. cenocepacia. Collectively, the data support the possibility of incorporating FliC T cell epitopes into vaccination programs targeting both at-risk individuals in B. pseudomallei endemic regions as well as CF patients.
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Affiliation(s)
- Julie A Musson
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, Tyne and Wear NE2 4HH, United Kingdom
| | - Catherine J Reynolds
- Section of Infectious Diseases and Immunity, Department of Medicine, Imperial College, London W12 0NN, United Kingdom
| | - Darawan Rinchai
- Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Arnone Nithichanon
- Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Prasong Khaenam
- Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Emmanuel Favry
- Commiseriat à l'Energie Atomique, Insititut de Biologie et de Technologies de Saclay, Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), 91191 Gif Sur Yvette, France; and
| | - Natasha Spink
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom
| | - Karen K Y Chu
- Section of Infectious Diseases and Immunity, Department of Medicine, Imperial College, London W12 0NN, United Kingdom
| | - Anthony De Soyza
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, Tyne and Wear NE2 4HH, United Kingdom
| | - Gregory J Bancroft
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom
| | - Ganjana Lertmemongkolchai
- Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Bernard Maillere
- Commiseriat à l'Energie Atomique, Insititut de Biologie et de Technologies de Saclay, Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), 91191 Gif Sur Yvette, France; and
| | - Rosemary J Boyton
- Section of Infectious Diseases and Immunity, Department of Medicine, Imperial College, London W12 0NN, United Kingdom
| | - Daniel M Altmann
- Section of Infectious Diseases and Immunity, Department of Medicine, Imperial College, London W12 0NN, United Kingdom
| | - John H Robinson
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, Tyne and Wear NE2 4HH, United Kingdom;
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Stone JK, DeShazer D, Brett PJ, Burtnick MN. Melioidosis: molecular aspects of pathogenesis. Expert Rev Anti Infect Ther 2014; 12:1487-99. [PMID: 25312349 DOI: 10.1586/14787210.2014.970634] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Burkholderia pseudomallei is a gram-negative bacterium that causes melioidosis, a multifaceted disease that is highly endemic in southeast Asia and northern Australia. This facultative intracellular pathogen possesses a large genome that encodes a wide array of virulence factors that promote survival in vivo by manipulating host cell processes and disarming elements of the host immune system. Antigens and systems that play key roles in B. pseudomallei virulence include capsular polysaccharide, lipopolysaccharide, adhesins, specialized secretion systems, actin-based motility and various secreted factors. This review provides an overview of the current and steadily expanding knowledge regarding the molecular mechanisms used by this organism to survive within a host and their contribution to the pathogenesis of melioidosis.
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Affiliation(s)
- Joshua K Stone
- Department of Microbiology and Immunology, University of South Alabama, 610 Clinic Drive, Mobile, AL 36688, USA
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Jitprasutwit S, Ong C, Juntawieng N, Ooi WF, Hemsley CM, Vattanaviboon P, Titball RW, Tan P, Korbsrisate S. Transcriptional profiles of Burkholderia pseudomallei reveal the direct and indirect roles of Sigma E under oxidative stress conditions. BMC Genomics 2014; 15:787. [PMID: 25214426 PMCID: PMC4175613 DOI: 10.1186/1471-2164-15-787] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Accepted: 09/08/2014] [Indexed: 11/12/2022] Open
Abstract
Background Burkholderia pseudomallei, the causative agent of melioidosis, is a Gram-negative bacterium widely distributed in soil and water in endemic areas. This soil saprophyte can survive harsh environmental conditions, even in soils where herbicides (containing superoxide generators) are abundant. Sigma factor E (σE) is a key regulator of extra-cytoplasmic stress response in Gram-negative bacteria. In this study, we identified the B. pseudomallei σE regulon and characterized the indirect role that σE plays in the regulation of spermidine, contributing to the successful survival of B. pseudomallei in stressful environments. Results Changes in the global transcriptional profiles of B. pseudomallei wild type and σE mutant under physiological and oxidative stress (hydrogen peroxide) conditions were determined. We identified 307 up-regulated genes under oxidative stress condition. Comparison of the transcriptional profiles of B. pseudomallei wild type and σE mutant under control or oxidative stress conditions identified 85 oxidative-responsive genes regulated by σE, including genes involved in cell membrane repair, maintenance of protein folding and oxidative stress response and potential virulence factors such as a type VI secretion system (T6SS). Importantly, we identified that the speG gene, encoding spermidine-acetyltransferase, is a novel member of the B. pseudomallei σE regulon. The expression of speG was regulated by σE, implying that σE plays an indirect role in the regulation of physiological level of spermidine to protect the bacteria during oxidative stress. Conclusion This study identified B. pseudomallei genes directly regulated by σE in response to oxidative stress and revealed the indirect role of σE in the regulation of the polyamine spermidine (via regulation of speG) for bacterial cell protection during oxidative stress. This study provides new insights into the regulatory mechanisms by which σE contributes to the survival of B. pseudomallei under stressful conditions. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-787) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Sunee Korbsrisate
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
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Cross-species comparison of the Burkholderia pseudomallei, Burkholderia thailandensis, and Burkholderia mallei quorum-sensing regulons. J Bacteriol 2014; 196:3862-71. [PMID: 25182491 DOI: 10.1128/jb.01974-14] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Burkholderia pseudomallei, Burkholderia thailandensis, and Burkholderia mallei (the Bptm group) are close relatives with very different lifestyles: B. pseudomallei is an opportunistic pathogen, B. thailandensis is a nonpathogenic saprophyte, and B. mallei is a host-restricted pathogen. The acyl-homoserine lactone quorum-sensing (QS) systems of these three species show a high level of conservation. We used transcriptome sequencing (RNA-seq) to define the quorum-sensing regulon in each species, and we performed a cross-species analysis of the QS-controlled orthologs. Our analysis revealed a core set of QS-regulated genes in all three species, as well as QS-controlled factors shared by only two species or unique to a given species. This global survey of the QS regulons of B. pseudomallei, B. thailandensis, and B. mallei serves as a platform for predicting which QS-controlled processes might be important in different bacterial niches and contribute to the pathogenesis of B. pseudomallei and B. mallei.
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56
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Chen Y, Schröder I, French CT, Jaroszewicz A, Yee XJ, Teh BE, Toesca IJ, Miller JF, Gan YH. Characterization and analysis of the Burkholderia pseudomallei BsaN virulence regulon. BMC Microbiol 2014; 14:206. [PMID: 25085508 PMCID: PMC4236580 DOI: 10.1186/s12866-014-0206-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 07/18/2014] [Indexed: 01/06/2023] Open
Abstract
Background Burkholderia pseudomallei is a facultative intracellular pathogen and the causative agent of melioidosis. A conserved type III secretion system (T3SS3) and type VI secretion system (T6SS1) are critical for intracellular survival and growth. The T3SS3 and T6SS1 genes are coordinately and hierarchically regulated by a TetR-type regulator, BspR. A central transcriptional regulator of the BspR regulatory cascade, BsaN, activates a subset of T3SS3 and T6SS1 loci. Results To elucidate the scope of the BsaN regulon, we used RNAseq analysis to compare the transcriptomes of wild-type B. pseudomallei KHW and a bsaN deletion mutant. The 60 genes positively-regulated by BsaN include those that we had previously identified in addition to a polyketide biosynthesis locus and genes involved in amino acid biosynthesis. BsaN was also found to repress the transcription of 51 genes including flagellar motility loci and those encoding components of the T3SS3 apparatus. Using a promoter-lacZ fusion assay in E. coli, we show that BsaN together with the chaperone BicA directly control the expression of the T3SS3 translocon, effector and associated regulatory genes that are organized into at least five operons (BPSS1516-BPSS1552). Using a mutagenesis approach, a consensus regulatory motif in the promoter regions of BsaN-regulated genes was shown to be essential for transcriptional activation. Conclusions BsaN/BicA functions as a central regulator of key virulence clusters in B. pseudomallei within a more extensive network of genetic regulation. We propose that BsaN/BicA controls a gene expression program that facilitates the adaption and intracellular survival of the pathogen within eukaryotic hosts.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Yunn-Hwen Gan
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore.
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Burtnick MN, Brett PJ, DeShazer D. Proteomic analysis of the Burkholderia pseudomallei type II secretome reveals hydrolytic enzymes, novel proteins, and the deubiquitinase TssM. Infect Immun 2014; 82:3214-26. [PMID: 24866793 PMCID: PMC4136222 DOI: 10.1128/iai.01739-14] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 05/10/2014] [Indexed: 12/25/2022] Open
Abstract
Burkholderia pseudomallei, the etiologic agent of melioidosis, is an opportunistic pathogen that harbors a wide array of secretion systems, including a type II secretion system (T2SS), three type III secretion systems (T3SS), and six type VI secretion systems (T6SS). The proteins exported by these systems provide B. pseudomallei with a growth advantage in vitro and in vivo, but relatively little is known about the full repertoire of exoproducts associated with each system. In this study, we constructed deletion mutations in gspD and gspE, T2SS genes encoding an outer membrane secretin and a cytoplasmic ATPase, respectively. The secretion profiles of B. pseudomallei MSHR668 and its T2SS mutants were noticeably different when analyzed by SDS-PAGE. We utilized liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify proteins present in the supernatants of B. pseudomallei MSHR668 and B. pseudomallei ΔgspD grown in rich and minimal media. The MSHR668 supernatants contained 48 proteins that were either absent or substantially reduced in the supernatants of ΔgspD strains. Many of these proteins were putative hydrolytic enzymes, including 12 proteases, two phospholipases, and a chitinase. Biochemical assays validated the LC-MS/MS results and demonstrated that the export of protease, phospholipase C, and chitinase activities is T2SS dependent. Previous studies had failed to identify the mechanism of secretion of TssM, a deubiquitinase that plays an integral role in regulating the innate immune response. Here we present evidence that TssM harbors an atypical signal sequence and that its secretion is mediated by the T2SS. This study provides the first in-depth characterization of the B. pseudomallei T2SS secretome.
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Affiliation(s)
- Mary N Burtnick
- Department of Microbiology and Immunology, University of South Alabama, Mobile, Alabama, USA
| | - Paul J Brett
- Department of Microbiology and Immunology, University of South Alabama, Mobile, Alabama, USA
| | - David DeShazer
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
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58
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Bacterial drug tolerance under clinical conditions is governed by anaerobic adaptation but not anaerobic respiration. Antimicrob Agents Chemother 2014; 58:5775-83. [PMID: 25049258 PMCID: PMC4187911 DOI: 10.1128/aac.02793-14] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Noninherited antibiotic resistance is a phenomenon whereby a subpopulation of genetically identical bacteria displays phenotypic tolerance to antibiotics. We show here that compared to Escherichia coli, the clinically relevant genus Burkholderia displays much higher levels of cells that tolerate ceftazidime. By measuring the dynamics of the formation of drug-tolerant cells under conditions that mimic in vivo infections, we show that in Burkholderia bacteria, oxygen levels affect the formation of these cells. The drug-tolerant cells are characterized by an anaerobic metabolic signature and can be eliminated by oxygenating the system or adding nitrate. The transcriptome profile suggests that these cells are not dormant persister cells and are likely to be drug tolerant as a consequence of the upregulation of anaerobic nitrate respiration, efflux pumps, β-lactamases, and stress response proteins. These findings have important implications for the treatment of chronic bacterial infections and the methodologies and conditions that are used to study drug-tolerant and persister cells in vitro.
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59
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Faison WJ, Rostovtsev A, Castro-Nallar E, Crandall KA, Chumakov K, Simonyan V, Mazumder R. Whole genome single-nucleotide variation profile-based phylogenetic tree building methods for analysis of viral, bacterial and human genomes. Genomics 2014; 104:1-7. [PMID: 24930720 DOI: 10.1016/j.ygeno.2014.06.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 06/04/2014] [Indexed: 10/25/2022]
Abstract
UNLABELLED Next-generation sequencing data can be mapped to a reference genome to identify single-nucleotide polymorphisms/variations (SNPs/SNVs; called SNPs hereafter). In theory, SNPs can be compared across several samples and the differences can be used to create phylogenetic trees depicting relatedness among the samples. However, in practice this is difficult because currently there is no stand-alone tool that takes SNP data directly as input and produces phylogenetic trees. In response to this need, PhyloSNP application was created with two analysis methods 1) a quantitative method that creates the presence/absence matrix which can be directly used to generate phylogenetic trees or creates a tree from a shrunk genome alignment (includes additional bases surrounding the SNP position) and 2) a qualitative method that clusters samples based on the frequency of different bases found at a particular position. The algorithms were used to generate trees from Poliovirus, Burkholderia and human cancer genomics NGS datasets. AVAILABILITY PhyloSNP is freely available for download at http://hive.biochemistry.gwu.edu/dna.cgi?cmd=phylosnp.
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Affiliation(s)
- William J Faison
- The Department of Biochemistry & Molecular Medicine, George Washington University Medical Center, Washington, DC 20037, USA.
| | - Alexandre Rostovtsev
- Center for Biologics Evaluation and Research, US Food and Drug Administration, 1451 Rockville Pike, Rockville, MD 20852, USA.
| | - Eduardo Castro-Nallar
- Computational Biology Institute, George Washington University, Ashburn, VA 20147, USA.
| | - Keith A Crandall
- Computational Biology Institute, George Washington University, Ashburn, VA 20147, USA.
| | - Konstantin Chumakov
- Center for Biologics Evaluation and Research, US Food and Drug Administration, 1451 Rockville Pike, Rockville, MD 20852, USA.
| | - Vahan Simonyan
- Center for Biologics Evaluation and Research, US Food and Drug Administration, 1451 Rockville Pike, Rockville, MD 20852, USA.
| | - Raja Mazumder
- The Department of Biochemistry & Molecular Medicine, George Washington University Medical Center, Washington, DC 20037, USA; McCormick Genomic and Proteomic Center, George Washington University, Washington, DC 20037, USA.
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Stubben CJ, Micheva-Viteva SN, Shou Y, Buddenborg SK, Dunbar JM, Hong-Geller E. Differential expression of small RNAs from Burkholderia thailandensis in response to varying environmental and stress conditions. BMC Genomics 2014; 15:385. [PMID: 24884623 PMCID: PMC4035088 DOI: 10.1186/1471-2164-15-385] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 05/06/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Bacterial small RNAs (sRNAs) regulate gene expression by base-pairing with downstream target mRNAs to attenuate translation of mRNA into protein at the post-transcriptional level. In response to specific environmental changes, sRNAs can modulate the expression levels of target genes, thus enabling adaptation of cellular physiology. RESULTS We profiled sRNA expression in the Gram-negative bacteria Burkholderia thailandensis cultured under 54 distinct growth conditions using a Burkholderia-specific microarray that contains probe sets to all intergenic regions greater than 90 bases. We identified 38 novel sRNAs and performed experimental validation on five sRNAs that play a role in adaptation of Burkholderia to cell stressors. In particular, the trans-encoded BTH_s1 and s39 exhibited differential expression profiles dependent on growth phase and cell stimuli, such as antibiotics and serum. Furthermore, knockdown of the highly-expressed BTH_s39 by antisense transcripts reduced B. thailandensis cell growth and attenuated host immune response upon infection, indicating that BTH_s39 functions in bacterial metabolism and adaptation to the host. In addition, expression of cis-encoded BTH_s13 and s19 found in the 5' untranslated regions of their cognate genes correlated with tight regulation of gene transcript levels. This sRNA-mediated downregulation of gene expression may be a conserved mechanism of post-transcriptional gene dosage control. CONCLUSIONS These studies provide a broad analysis of differential Burkholderia sRNA expression profiles and illustrate the complexity of bacterial gene regulation in response to different environmental stress conditions.
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Peano C, Chiaramonte F, Motta S, Pietrelli A, Jaillon S, Rossi E, Consolandi C, Champion OL, Michell SL, Freddi L, Falciola L, Basilico F, Garlanda C, Mauri P, De Bellis G, Landini P. Gene and protein expression in response to different growth temperatures and oxygen availability in Burkholderia thailandensis. PLoS One 2014; 9:e93009. [PMID: 24671187 PMCID: PMC3966863 DOI: 10.1371/journal.pone.0093009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 02/27/2014] [Indexed: 12/25/2022] Open
Abstract
Burkholderia thailandensis, although normally avirulent for mammals, can infect macrophages in vitro and has occasionally been reported to cause pneumonia in humans. It is therefore used as a model organism for the human pathogen B. pseudomallei, to which it is closely related phylogenetically. We characterized the B. thailandensis clinical isolate CDC2721121 (BtCDC272) at the genome level and studied its response to environmental cues associated with human host colonization, namely, temperature and oxygen limitation. Effects of the different growth conditions on BtCDC272 were studied through whole genome transcription studies and analysis of proteins associated with the bacterial cell surface. We found that growth at 37°C, compared to 28°C, negatively affected cell motility and flagella production through a mechanism involving regulation of the flagellin-encoding fliC gene at the mRNA stability level. Growth in oxygen-limiting conditions, in contrast, stimulated various processes linked to virulence, such as lipopolysaccharide production and expression of genes encoding protein secretion systems. Consistent with these observations, BtCDC272 grown in oxygen limitation was more resistant to phagocytosis and strongly induced the production of inflammatory cytokines from murine macrophages. Our results suggest that, while temperature sensing is important for regulation of B. thailandensis cell motility, oxygen limitation has a deeper impact on its physiology and constitutes a crucial environmental signal for the production of virulence factors.
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Affiliation(s)
- Clelia Peano
- Institute of Biomedical Technologies, National Research Council, Segrate, Milan, Italy
| | | | - Sara Motta
- Institute of Biomedical Technologies, National Research Council, Segrate, Milan, Italy
| | - Alessandro Pietrelli
- Institute of Biomedical Technologies, National Research Council, Segrate, Milan, Italy
| | - Sebastien Jaillon
- Humanitas Clinical and Research Center Institute, Rozzano, Milan, Italy
| | - Elio Rossi
- Department of Biosciences, Università degli Studi di Milano, Milan, Italy
| | - Clarissa Consolandi
- Institute of Biomedical Technologies, National Research Council, Segrate, Milan, Italy
| | - Olivia L. Champion
- College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Stephen L. Michell
- College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Luca Freddi
- Department of Biosciences, Università degli Studi di Milano, Milan, Italy
| | - Luigi Falciola
- Department of Chemistry, Università degli Studi di Milano, Milan, Italy
| | - Fabrizio Basilico
- Institute of Biomedical Technologies, National Research Council, Segrate, Milan, Italy
| | - Cecilia Garlanda
- Humanitas Clinical and Research Center Institute, Rozzano, Milan, Italy
| | - Pierluigi Mauri
- Institute of Biomedical Technologies, National Research Council, Segrate, Milan, Italy
| | - Gianluca De Bellis
- Institute of Biomedical Technologies, National Research Council, Segrate, Milan, Italy
| | - Paolo Landini
- Department of Biosciences, Università degli Studi di Milano, Milan, Italy
- * E-mail:
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The Type VI secretion system spike protein VgrG5 mediates membrane fusion during intercellular spread by pseudomallei group Burkholderia species. Infect Immun 2014; 82:1436-44. [PMID: 24421040 DOI: 10.1128/iai.01367-13] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Pseudomallei group Burkholderia species are facultative intracellular parasites that spread efficiently from cell to cell by a mechanism involving the fusion of adjacent cell membranes. Intercellular fusion requires the function of the cluster 5 type VI secretion system (T6SS-5) and its associated valine-glycine repeat protein, VgrG5. Here we show that VgrG5 alleles are conserved and functionally interchangeable between Burkholderia pseudomallei and its relatives B. mallei, B. oklahomensis, and B. thailandensis. We also demonstrate that the integrity of the VgrG5 C-terminal domain is required for fusogenic activity, and we identify sequence motifs, including two hydrophobic segments, that are important for fusion. Mutagenesis and secretion experiments using B. pseudomallei strains engineered to express T6SS-5 in vitro show that the VgrG5 C-terminal domain is dispensable for T6SS-mediated secretion of Hcp5, demonstrating that the ability of VgrG5 to mediate membrane fusion can be uncoupled from its essential role in type VI secretion. We propose a model in which a unique fusogenic activity at the C terminus of VgrG5 facilitates intercellular spread by B. pseudomallei and related species following injection across the plasma membranes of infected cells.
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