• Dual Role of the Adaptive Immune System in Liver Injury and Hepatocellular Carcinoma Development.

      Endig, Jessica; Buitrago-Molina, Laura Elisa; Marhenke, Silke; Reisinger, Florian; Saborowski, Anna; Schütt, Jutta; Limbourg, Florian; Könecke, Christian; Schreder, Alina; Michael, Alina; et al. (2016-08-08)
      Hepatocellular carcinoma (HCC) represents a classic example of inflammation-linked cancer. To characterize the role of the immune system in hepatic injury and tumor development, we comparatively studied the extent of liver disease and hepatocarcinogenesis in immunocompromised versus immunocompetent Fah-deficient mice. Strikingly, chronic liver injury and tumor development were markedly suppressed in alymphoid Fah(-/-) mice despite an overall increased mortality. Mechanistically, we show that CD8(+) T cells and lymphotoxin β are central mediators of HCC formation. Antibody-mediated depletion of CD8(+) T cells as well as pharmacological inhibition of the lymphotoxin-β receptor markedly delays tumor development in mice with chronic liver injury. Thus, our study unveils distinct functions of the immune system, which are required for liver regeneration, survival, and hepatocarcinogenesis.
    • Dysbiosis in chronic periodontitis: Key microbial players and interactions with the human host.

      Deng, Zhi-Luo; Szafrański, Szymon P; Jarek, Michael; Bhuju, Sabin; Wagner-Döbler, Irene; Helmholtz Centre for infection research, Inhoffenstr. 7., 38124 Braunschweig, Germany. (2017-06-16)
      Periodontitis is an extremely prevalent disease worldwide and is driven by complex dysbiotic microbiota. Here we analyzed the transcriptional activity of the periodontal pocket microbiota from all domains of life as well as the human host in health and chronic periodontitis. Bacteria showed strong enrichment of 18 KEGG functional modules in chronic periodontitis, including bacterial chemotaxis, flagellar assembly, type III secretion system, type III CRISPR-Cas system, and two component system proteins. Upregulation of these functions was driven by the red-complex pathogens and candidate pathogens, e.g. Filifactor alocis, Prevotella intermedia, Fretibacterium fastidiosum and Selenomonas sputigena. Nine virulence factors were strongly up-regulated, among them the arginine deiminase arcA from Porphyromonas gingivalis and Mycoplasma arginini. Viruses and archaea accounted for about 0.1% and 0.22% of total putative mRNA reads, respectively, and a protozoan, Entamoeba gingivalis, was highly enriched in periodontitis. Fourteen human transcripts were enriched in periodontitis, including a gene for a ferric iron binding protein, indicating competition with the microbiota for iron, and genes associated with cancer, namely nucleolar phosphoprotein B23, ankyrin-repeat domain 30B-like protein and beta-enolase. The data provide evidence on the level of gene expression in vivo for the potentially severe impact of the dysbiotic microbiota on human health.
    • Dysregulated serum response factor triggers formation of hepatocellular carcinoma.

      Ohrnberger, Stefan; Thavamani, Abhishek; Braeuning, Albert; Lipka, Daniel B; Kirilov, Milen; Geffers, Robert; Authenrieth, Stella E; Römer, Michael; Zell, Andreas; Bonin, Michael; et al. (2015-03)
      The ubiquitously expressed transcriptional regulator serum response factor (SRF) is controlled by both Ras/MAPK (mitogen-activated protein kinase) and Rho/actin signaling pathways, which are frequently activated in hepatocellular carcinoma (HCC). We generated SRF-VP16(iHep) mice, which conditionally express constitutively active SRF-VP16 in hepatocytes, thereby controlling subsets of both Ras/MAPK- and Rho/actin-stimulated target genes. All SRF-VP16(iHep) mice develop hyperproliferative liver nodules that progresses to lethal HCC. Some murine (m)HCCs acquire Ctnnb1 mutations equivalent to those in human (h)HCC. The resulting transcript signatures mirror those of a distinct subgroup of hHCCs, with shared activation of oncofetal genes including Igf2, correlating with CpG hypomethylation at the imprinted Igf2/H19 locus.
    • Effects of green tea compound epigallocatechin-3-gallate against Stenotrophomonas maltophilia infection and biofilm.

      Vidigal, Pedrina G; Müsken, Mathias; Becker, Katrin A; Häussler, Susanne; Wingender, Jost; Steinmann, Eike; Kehrmann, Jan; Gulbins, Erich; Buer, Jan; Rath, Peter Michael; et al. (2014)
      We investigated the in vitro and in vivo activities of epigallocatechin-3-gallate (EGCg), a green tea component, against Stenotrophomonas maltophilia (Sm) isolates from cystic fibrosis (CF) patients. In vitro effects of EGCg and the antibiotic colistin (COL) on growth inhibition, survival, and also against young and mature biofilms of S. maltophilia were determined. Qualitative and quantitative changes on the biofilms were assessed by confocal laser scanning microscopy (CLSM). Further, in vivo effects of nebulized EGCg in C57BL/6 and Cftr mutant mice during acute Sm lung infection were evaluated. Subinhibitory concentrations of EGCg significantly reduced not only biofilm formation, but also the quantity of viable cells in young and mature biofilms. CLSM showed that EGCg-exposed biofilms exhibited either a change in total biofilm biovolume or an increase of the fraction of dead cells contained within the biofilm in a dose depended manner. Sm infected wild-type and Cftr mutant mice treated with 1,024 mg/L EGCg by inhalation exhibited significantly lower bacterial counts than those undergoing no treatment or treated with COL. EGCg displayed promising inhibitory and anti-biofilm properties against CF Sm isolates in vitro and significantly reduced Sm bacterial counts in an acute infection model with wild type and CF mice. This natural compound may represent a novel therapeutic agent against Sm infection in CF.
    • Effects of Type I Interferons on Friend Retrovirus Infection

      Gerlach, Nicole; Schimmer, Simone; Weiss, Siegfried; Kalinke, Ulrich; Dittmer, Ulf (American Society for Microbiology, 2006-04)
    • Efficiency of Conditionally Attenuated Salmonella enterica Serovar Typhimurium in Bacterium-Mediated Tumor Therapy.

      Frahm, Michael; Felgner, Sebastian; Kocijancic, Dino; Rohde, M; Hensel, Michael; Curtiss, Roy; Erhardt, Marc; Weiss, Siegfried; Helmholtz Centre for Infection Research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2015)
      Increasing numbers of cancer cases generate a great urge for new treatment options. Applying bacteria like Salmonella enterica serovar Typhimurium for cancer therapy represents an intensively explored option. These bacteria have been shown not only to colonize solid tumors but also to exhibit an intrinsic antitumor effect. In addition, they could serve as tumor-targeting vectors for therapeutic molecules. However, the pathogenic S. Typhimurium strains used for tumor therapy need to be attenuated for safe application. Here, lipopolysaccharide (LPS) deletion mutants (ΔrfaL, ΔrfaG, ΔrfaH, ΔrfaD, ΔrfaP, and ΔmsbB mutants) of Salmonella were investigated for efficiency in tumor therapy. Of such variants, the ΔrfaD and ΔrfaG deep rough mutants exhibited the best tumor specificity and lowest pathogenicity. However, the intrinsic antitumor effect was found to be weak. To overcome this limitation, conditional attenuation was tested by complementing the mutants with an inducible arabinose promoter. The chromosomal integration of the respective LPS biosynthesis genes into the araBAD locus exhibited the best balance of attenuation and therapeutic benefit. Thus, the present study establishes a basis for the development of an applicably cancer therapeutic bacterium.
    • Efficient Replication of the Novel Human Betacoronavirus EMC on Primary Human Epithelium Highlights Its Zoonotic Potential.

      Kindler, Eveline; Jónsdóttir, Hulda R; Muth, Doreen; Hamming, Ole J; Hartmann, Rune; Rodriguez, Regulo; Geffers, Robert; Fouchier, Ron A M; Drosten, Christian; Müller, Marcel A; et al. (2013)
      ABSTRACT The recent emergence of a novel human coronavirus (HCoV-EMC) in the Middle East raised considerable concerns, as it is associated with severe acute pneumonia, renal failure, and fatal outcome and thus resembles the clinical presentation of severe acute respiratory syndrome (SARS) observed in 2002 and 2003. Like SARS-CoV, HCoV-EMC is of zoonotic origin and closely related to bat coronaviruses. The human airway epithelium (HAE) represents the entry point and primary target tissue for respiratory viruses and is highly relevant for assessing the zoonotic potential of emerging respiratory viruses, such as HCoV-EMC. Here, we show that pseudostratified HAE cultures derived from different donors are highly permissive to HCoV-EMC infection, and by using reverse transcription (RT)-PCR and RNAseq data, we experimentally determined the identity of seven HCoV-EMC subgenomic mRNAs. Although the HAE cells were readily responsive to type I and type III interferon (IFN), we observed neither a pronounced inflammatory cytokine nor any detectable IFN responses following HCoV-EMC, SARS-CoV, or HCoV-229E infection, suggesting that innate immune evasion mechanisms and putative IFN antagonists of HCoV-EMC are operational in the new host. Importantly, however, we demonstrate that both type I and type III IFN can efficiently reduce HCoV-EMC replication in HAE cultures, providing a possible treatment option in cases of suspected HCoV-EMC infection. IMPORTANCE A novel human coronavirus, HCoV-EMC, has recently been described to be associated with severe respiratory tract infection and fatalities, similar to severe acute respiratory syndrome (SARS) observed during the 2002-2003 epidemic. Closely related coronaviruses replicate in bats, suggesting that, like SARS-CoV, HCoV-EMC is of zoonotic origin. Since the animal reservoir and circumstances of zoonotic transmission are yet elusive, it is critically important to assess potential species barriers of HCoV-EMC infection. An important first barrier against invading respiratory pathogens is the epithelium, representing the entry point and primary target tissue of respiratory viruses. We show that human bronchial epithelia are highly susceptible to HCoV-EMC infection. Furthermore, HCoV-EMC, like other coronaviruses, evades innate immune recognition, reflected by the lack of interferon and minimal inflammatory cytokine expression following infection. Importantly, type I and type III interferon treatment can efficiently reduce HCoV-EMC replication in the human airway epithelium, providing a possible avenue for treatment of emerging virus infections.
    • Elucidation of Sigma Factor-Associated Networks in Pseudomonas aeruginosa Reveals a Modular Architecture with Limited and Function-Specific Crosstalk.

      Schulz, Sebastian; Eckweiler, Denitsa; Bielecka, Agata; Nicolai, Tanja; Franke, Raimo; Dötsch, Andreas; Hornischer, Klaus; Bruchmann, Sebastian; Düvel, Juliane; Häussler, Susanne; et al. (2015-03)
      Sigma factors are essential global regulators of transcription initiation in bacteria which confer promoter recognition specificity to the RNA polymerase core enzyme. They provide effective mechanisms for simultaneously regulating expression of large numbers of genes in response to challenging conditions, and their presence has been linked to bacterial virulence and pathogenicity. In this study, we constructed nine his-tagged sigma factor expressing and/or deletion mutant strains in the opportunistic pathogen Pseudomonas aeruginosa. To uncover the direct and indirect sigma factor regulons, we performed mRNA profiling, as well as chromatin immunoprecipitation coupled to high-throughput sequencing. We furthermore elucidated the de novo binding motif of each sigma factor, and validated the RNA- and ChIP-seq results by global motif searches in the proximity of transcriptional start sites (TSS). Our integrated approach revealed a highly modular network architecture which is composed of insulated functional sigma factor modules. Analysis of the interconnectivity of the various sigma factor networks uncovered a limited, but highly function-specific, crosstalk which orchestrates complex cellular processes. Our data indicate that the modular structure of sigma factor networks enables P. aeruginosa to function adequately in its environment and at the same time is exploited to build up higher-level functions by specific interconnections that are dominated by a participation of RpoN.
    • Enantiomer-specific and paracrine leukemogenicity of mutant IDH metabolite 2-hydroxyglutarate.

      Chaturvedi, A; Araujo Cruz, M M; Jyotsana, N; Sharma, A; Goparaju, R; Schwarzer, A; Görlich, K; Schottmann, R; Struys, E A; Jansen, E E; et al. (2016-08)
      Canonical mutations in IDH1 and IDH2 produce high levels of the R-enantiomer of 2-hydroxyglutarate (R-2HG), which is a competitive inhibitor of α-ketoglutarate (αKG)-dependent enzymes and a putative oncometabolite. Mutant IDH1 collaborates with HoxA9 to induce monocytic leukemia in vivo. We used two mouse models and a patient-derived acute myeloid leukemia xenotransplantation (PDX) model to evaluate the in vivo transforming potential of R-2HG, S-2HG and αKG independent of the mutant IDH1 protein. We show that R-2HG, but not S-2HG or αKG, is an oncometabolite in vivo that does not require the mutant IDH1 protein to induce hyperleukocytosis and to accelerate the onset of murine and human leukemia. Thus, circulating R-2HG acts in a paracrine manner and can drive the expansion of many different leukemic and preleukemic clones that may express wild-type IDH1, and therefore can be a driver of clonal evolution and diversity. In addition, we show that the mutant IDH1 protein is a stronger oncogene than R-2HG alone when comparable intracellular R-2HG levels are achieved. We therefore propose R-2HG-independent oncogenic functions of mutant IDH1 that may need to be targeted in addition to R-2HG production to exploit the full therapeutic potential of IDH1 inhibition.
    • Engineered Salmonella enterica serovar Typhimurium overcomes limitations of anti-bacterial immunity in bacteria-mediated tumor therapy

      Felgner, Sebastian; Kocijancic, Dino; Frahm, Michael; Heise, Ulrike; Rohde, Manfred; Zimmermann, Kurt; Falk, Christine; Erhardt, Marc; Weiss, Siegfried; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany.; et al. (2017-09-29)
    • Establishment of an induced memory response in Pseudomonas aeruginosa during infection of a eukaryotic host.

      Kordes, Adrian; Grahl, Nora; Koska, Michal; Preusse, Matthias; Arce-Rodriguez, Alejandro; Abraham, Wolf-Rainer; Kaever, Volkhard; Häussler, Susanne; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Springer-Nature, 2019-08-01)
      In a given habitat, bacterial cells often experience recurrent exposures to the same environmental stimulus. The ability to memorize the past event and to adjust current behaviors can lead to efficient adaptation to the recurring stimulus. Here we demonstrate that the versatile bacterium Pseudomonas aeruginosa adopts a virulence phenotype after serial passage in the invertebrate model host Galleria mellonella. The virulence phenotype was not linked to the acquisition of genetic variations and was sustained for several generations, despite cultivation of the ex vivo virulence-adapted P. aeruginosa cells under rich medium conditions in vitro. Transcriptional reprogramming seemed to be induced by a host-specific food source, as reprogramming was also observed upon cultivation of P. aeruginosa in rich medium supplemented with polyunsaturated long-chain fatty acids. The establishment of induced memory responses adds a time dimension and seems to fill the gap between long-term evolutionary genotypic adaptation and short-term induced individual responses. Efforts to unravel the fundamental mechanisms that underlie the carry-over effect to induce such memory responses will continue to be of importance as hysteretic behavior can serve survival of bacterial populations in changing and challenging habitats.
    • Evaluation of a microarray-hybridization based method applicable for discovery of single nucleotide polymorphisms (SNPs) in the Pseudomonas aeruginosa genome

      Dötsch, Andreas; Pommerenke, Claudia; Bredenbruch, Florian; Geffers, Robert; Häussler, Susanne (2009-01-19)
      Abstract Background Whole genome sequencing techniques have added a new dimension to studies on bacterial adaptation, evolution and diversity in chronic infections. By using this powerful approach it was demonstrated that Pseudomonas aeruginosa undergoes intense genetic adaptation processes, crucial in the development of persistent disease. The challenge ahead is to identify universal infection relevant adaptive bacterial traits as potential targets for the development of alternative treatment strategies. Results We developed a microarray-based method applicable for discovery of single nucleotide polymorphisms (SNPs) in P. aeruginosa as an easy and economical alternative to whole genome sequencing. About 50% of all SNPs theoretically covered by the array could be detected in a comparative hybridization of PAO1 and PA14 genomes at high specificity (> 0.996). Variations larger than SNPs were detected at much higher sensitivities, reaching nearly 100% for genetic differences affecting multiple consecutive probe oligonucleotides. The detailed comparison of the in silico alignment with experimental hybridization data lead to the identification of various factors influencing sensitivity and specificity in SNP detection and to the identification of strain specific features such as a large deletion within the PA4684 and PA4685 genes in the Washington Genome Center PAO1. Conclusion The application of the genome array as a tool to identify adaptive mutations, to depict genome organizations, and to identify global regulons by the "ChIP-on-chip" technique will expand our knowledge on P. aeruginosa adaptation, evolution and regulatory mechanisms of persistence on a global scale and thus advance the development of effective therapies to overcome persistent disease.
    • Evaluation of latent tuberculosis infection in patients with inflammatory arthropathies before treatment with TNF-alpha blocking drugs using a novel flow-cytometric interferon-gamma release assay.

      Dinser, R; Fousse, M; Sester, U; Albrecht, K; Singh, M; Köhler, H; Müller-Ladner, U; Sester, M; Department of Internal Medicine and Rheumatology, Justus-Liebig University of Giessen, Kerckhoff Clinic, Benekestrasse 2-8, D-61231 Bad Nauheim, Germany. r.dinser@kerckhoff-klinik.de (2008-02)
      OBJECTIVE: To compare the efficacy of the conventional skin test and a novel flow cytometric whole blood assay in the diagnosis of latent tuberculosis infection (LTBI) in patients with rheumatological diseases evaluated for treatment with TNF-alpha-blocking agents. METHODS: Prospective study of 97 consecutively enrolled patients, who were assessed for the presence of LTBI through clinical history, Mendel-Mantoux skin testing and chest X-ray. In addition, T-cell reactivity towards tuberculin (PPD, purified protein derivative) and the Mycobacterium tuberculosis-specific proteins ESAT-6 and CFP-10 was determined ex vivo using a flow cytometric whole blood assay. RESULTS: After standard screening, 15% of patients receiving TNF-alpha-blocking therapy were pretreated with isoniazide (INH), another 5% of patients did not receive TNF-alpha-blocking therapy because of LTBI. PPD-reactivity in the skin was observed in 14% of patients compared with 39% with the whole blood test. Analysis of the M. tuberculosis-specific response to ESAT-6 and CFP-10 revealed positive results in 16% of patients. Using a decision tree incorporating history, chest X-ray and either skin-test or ESAT-6/CFP-10 results, 18 or 22% of the patients, respectively, were classified as latently infected with M. tuberculosis. Four patients treated with INH because of a positive skin reaction did not show reactivity to ESAT-6/CFP-10 in the whole blood assays. Another six patients not pretreated with INH because of negative skin tests would have received INH, had the results of the whole blood assay been taken into account. CONCLUSION: The Mendel-Mantoux skin test has a low sensitivity and specificity for the diagnosis of LTBI in this cohort of patients, potentially resulting in both over- and under-treatment with prophylactic INH when compared with the flow cytometric analysis of whole blood T-cell reactivity to proteins specific to M. tuberculosis. Use of T-cell based in vitro tests may help to refine diagnostic testing for LTBI.
    • Evolutionary conservation of essential and highly expressed genes in Pseudomonas aeruginosa.

      Dötsch, Andreas; Klawonn, Frank; Jarek, Michael; Scharfe, Maren; Blöcker, Helmut; Häussler, Susanne; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2010)
      The constant increase in development and spread of bacterial resistance to antibiotics poses a serious threat to human health. New sequencing technologies are now on the horizon that will yield massive increases in our capacity for DNA sequencing and will revolutionize the drug discovery process. Since essential genes are promising novel antibiotic targets, the prediction of gene essentiality based on genomic information has become a major focus.
    • Ex vivo transcriptional profiling reveals a common set of genes important for the adaptation of Pseudomonas aeruginosa to chronically infected host sites.

      Bielecki, Piotr; Komor, Uliana; Bielecka, Agata; Müsken, Mathias; Puchałka, Jacek; Pletz, Mathias W; Ballmann, Manfred; Martins dos Santos, Vítor A P; Weiss, Siegfried; Häussler, Susanne; et al. (2013-02)
      The opportunistic bacterium Pseudomonas aeruginosa is a major nosocomial pathogen causing both devastating acute and chronic persistent infections. During the course of an infection, P.  aeruginosa rapidly adapts to the specific conditions within the host. In the present study, we aimed at the identification of genes that are highly expressed during biofilm infections such as in chronically infected lungs of patients with cystic fibrosis (CF), burn wounds and subcutaneous mouse tumours. We found a common subset of differentially regulated genes in all three in vivo habitats and evaluated whether their inactivation impacts on the bacterial capability to form biofilms in vitro and to establish biofilm-associated infections in a murine model. Additive effects on biofilm formation and host colonization were discovered by the combined inactivation of several highly expressed genes. However, even combined inactivation was not sufficient to abolish the establishment of an infection completely. These findings can be interpreted as evidence that either redundant traits encode functions that are essential for in vivo survival and chronic biofilm infections and/or bacterial adaptation is considerably achieved independently of transcription levels. Supplemental screens, will have to be applied in order to identify the minimal set of key genes essential for the establishment of chronic infectious diseases.
    • Exome sequencing and case-control analyses identify RCC1 as a candidate breast cancer susceptibility gene.

      Riahi, Aouatef; Radmanesh, Hoda; Schürmann, Peter; Bogdanova, Natalia; Geffers, Robert; Meddeb, Rym; Kharrat, Maher; Dörk, Thilo; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018-06-15)
      Breast cancer is a genetic disease but the known genes explain a minority of cases. To elucidate the molecular basis of breast cancer in the Tunisian population, we performed exome sequencing on six BRCA1/BRCA2 mutation-negative patients with familial breast cancer and identified a novel frameshift mutation in RCC1, encoding the Regulator of Chromosome Condensation 1. Subsequent genotyping detected the 19-bp deletion in additional 5 out of 153 (3%) breast cancer patients but in none of 400 female controls (p = 0.0015). The deletion was enriched in patients with a positive family history (5%, p = 0.0009) and co-segregated with breast cancer in the initial pedigree. The mutant allele was lost in 4/6 breast tumors from mutation carriers which may be consistent with the hypothesis that RCC1 dysfunction provides a selective disadvantage at the stage of tumor progression. In summary, we propose RCC1 as a likely breast cancer susceptibility gene in the Tunisian population.
    • Expanding the TRANSFAC database towards an expert system of regulatory molecular mechanisms.

      Heinemeyer, T; Chen, X; Karas, H; Kel, A E; Kel, O V; Liebich, I; Meinhardt, T; Reuter, I; Schacherer, F; Wingender, E (1999-01-01)
    • Expression of the MexXY aminoglycoside efflux pump and presence of an aminoglycoside modifying enzyme in clinical isolates are highly correlated.

      Seupt, Alexander; Schniederjans, Monika; Tomasch, Jürgen; Häussler, Susanne; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (ASM, 2020-10-12)
      The impact of MexXY efflux pump expression on aminoglycoside resistance in clinical Pseudomonas aeruginosa isolates has been debated. In this study, we found that in general, elevated mexXY gene expression levels in clinical P. aeruginosa isolates confer to slight increases in aminoglycoside MIC levels, however those levels rarely lead to clinically relevant resistance phenotypes. The main driver of resistance in the clinical isolates studied here was the acquisition of aminoglycoside modifying enzymes (AMEs). Nevertheless, acquisition of an AME was strongly associated with mexY overexpression. In line with this observation, we demonstrate that the introduction of a gentamicin acetyl-transferase confers to full gentamicin resistance levels in a P. aeruginosa type strain only if the MexXY efflux pump was active. We discuss that increased mexXY activity in clinical AME harboring P. aeruginosa isolates might affect ion fluxes at the bacterial cell membrane and thus might play a role in the establishment of enhanced fitness that extends beyond aminoglycoside resistance.
    • An extended transcriptional regulatory network of Escherichia coli and analysis of its hierarchical structure and network motifs

      Ma, Hong-Wu; Kumar, Bharani; Ditges, Uta; Gunzer, Florian; Buer, Jan; Zeng, An-Ping (Oxford University Press, 2004)
    • The extensive set of accessory Pseudomonas aeruginosa genomic components.

      Pohl, Sarah; Klockgether, Jens; Eckweiler, Denitsa; Khaledi, Ariane; Schniederjans, Monika; Chouvarine, Philippe; Tümmler, Burkhard; Häussler, Susanne (2014-07)
      Up to 20% of the chromosomal Pseudomonas aeruginosa DNA belong to the so-called accessory genome. Its elements are specific for subgroups or even single strains and are likely acquired by horizontal gene transfer (HGT). Similarities of the accessory genomic elements to DNA from other bacterial species, mainly the DNA of γ- and β-proteobacteria, indicate a role of interspecies HGT. In this study, we analysed the expression of the accessory genome in 150 clinical P. aeruginosa isolates as uncovered by transcriptome sequencing and the presence of accessory genes in eleven additional isolates. Remarkably, despite the large number of P. aeruginosa strains that have been sequenced to date, we found new strain-specific compositions of accessory genomic elements and a high portion (10-20%) of genes without P. aeruginosa homologues. Although some genes were detected to be expressed/present in several isolates, individual patterns regarding the genes, their functions and the possible origin of the DNA were widespread among the tested strains. Our results demonstrate the unaltered potential to discover new traits within the P. aeruginosa population and underline that the P. aeruginosa pangenome is likely to increase with increasing sequence information.