• Genetic tools for the investigation of Roseobacter clade bacteria.

      Piekarski, Tanja; Buchholz, Ina; Drepper, Thomas; Schobert, Max; Wagner-Doebler, Irene; Tielen, Petra; Jahn, Dieter (2009)
      The Roseobacter clade represents one of the most abundant, metabolically versatile and ecologically important bacterial groups found in marine habitats. A detailed molecular investigation of the regulatory and metabolic networks of these organisms is currently limited for many strains by missing suitable genetic tools.
    • Genetic variability of mutans streptococci revealed by wide whole-genome sequencing.

      Song, Lifu; Wang, Wei; Conrads, Georg; Rheinberg, Anke; Sztajer, Helena; Reck, Michael; Wagner-Döbler, Irene; Zeng, An-Ping; Institute of Bioprocess and Biosystems, Technical University Hamburg Harburg, Hamburg Harburg, Germany. (2013)
      Mutans streptococci are a group of bacteria significantly contributing to tooth decay. Their genetic variability is however still not well understood.
    • Genome of the marine alphaproteobacterium Hoeflea phototrophica type strain (DFL-43T)

      Fiebig, Anne; Pradella, Silke; Petersen, Jörn; Michael, Victoria; Päuker, Orsola; Rohde, Manfred; Göker, Markus; Klenk, Hans-Peter; Wagner-Döbler, Irene (2013)
    • Genome of the R-body producing marine alphaproteobacterium Labrenzia alexandrii type strain (DFL-11(T)).

      Fiebig, Anne; Pradella, Silke; Petersen, Jörn; Päuker, Orsola; Michael, Victoria; Lünsdorf, Heinrich; Göker, Markus; Klenk, Hans-Peter; Wagner-Döbler, Irene (2013)
      Labrenzia alexandrii Biebl et al. 2007 is a marine member of the family Rhodobacteraceae in the order Rhodobacterales, which has thus far only partially been characterized at the genome level. The bacterium is of interest because it lives in close association with the toxic dinoflagellate Alexandrium lusitanicum. Ultrastructural analysis reveals R-bodies within the bacterial cells, which are primarily known from obligate endosymbionts that trigger "killing traits" in ciliates (Paramecium spp.). Genomic traits of L. alexandrii DFL-11(T) are in accordance with these findings, as they include the reb genes putatively involved in R-body synthesis. Analysis of the two extrachromosomal elements suggests a role in heavy-metal resistance and exopolysaccharide formation, respectively. The 5,461,856 bp long genome with its 5,071 protein-coding and 73 RNA genes consists of one chromosome and two plasmids, and has been sequenced in the context of the Marine Microbial Initiative.
    • Genome Organization and Localization of the pufLM Genes of the Photosynthesis Reaction Center in Phylogenetically Diverse Marine Alphaproteobacteria

      Pradella, Silke; Allgaier, Martin; Hoch, Christa; Päuker, Orsola; Stackebrandt, Erko; Wagner-Döbler, Irene (American Society for Microbiology, 2004-06)
    • Genome sequence of the reddish-pigmented Rubellimicrobium thermophilum type strain (DSM 16684T), a member of the Roseobacter clade

      Fiebig, Anne; Riedel, Thomas; Gronow, Sabine; Petersen, Jörn; Klenk, Hans-Peter; Göker, Markus; reseach group microbial communication, Helmholtz Centre for infection research, D-38124 Braunschweig, Germany (2014-05-15)
    • A genome-wide study of two-component signal transduction systems in eight newly sequenced mutans streptococci strains

      Song, Lifu; Sudhakar, Padhmanand; Wang, Wei; Conrads, Georg; Brock, Anke; Sun, Jibin; Wagner-Döbler, Irene; Zeng, An-Ping (2012-04-04)
      Abstract Background Mutans streptococci are a group of gram-positive bacteria including the primary cariogenic dental pathogen Streptococcus mutans and closely related species. Two component systems (TCSs) composed of a signal sensing histidine kinase (HK) and a response regulator (RR) play key roles in pathogenicity, but have not been comparatively studied for these oral bacterial pathogens. Results HKs and RRs of 8 newly sequenced mutans streptococci strains, including S. sobrinus DSM20742, S. ratti DSM20564 and six S. mutans strains, were identified and compared to the TCSs of S. mutans UA159 and NN2025, two previously genome sequenced S. mutans strains. Ortholog analysis revealed 18 TCS clusters (HK-RR pairs), 2 orphan HKs and 2 orphan RRs, of which 8 TCS clusters were common to all 10 strains, 6 were absent in one or more strains, and the other 4 were exclusive to individual strains. Further classification of the predicted HKs and RRs revealed interesting aspects of their putative functions. While TCS complements were comparable within the six S. mutans strains, S. sobrinus DSM20742 lacked TCSs possibly involved in acid tolerance and fructan catabolism, and S. ratti DSM20564 possessed 3 unique TCSs but lacked the quorum-sensing related TCS (ComDE). Selected computational predictions were verified by PCR experiments. Conclusions Differences in the TCS repertoires of mutans streptococci strains, especially those of S. sobrinus and S. ratti in comparison to S. mutans, imply differences in their response mechanisms for survival in the dynamic oral environment. This genomic level study of TCSs should help in understanding the pathogenicity of these mutans streptococci strains.
    • A genome-wide study of two-component signal transduction systems in eight newly sequenced mutans streptococci strains.

      Song, Lifu; Sudhakar, Padhmanand; Wang, Wei; Conrads, Georg; Brock, Anke; Sun, Jibin; Wagner-Döbler, Irene; Zeng, An-Ping; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2012)
      Mutans streptococci are a group of gram-positive bacteria including the primary cariogenic dental pathogen Streptococcus mutans and closely related species. Two component systems (TCSs) composed of a signal sensing histidine kinase (HK) and a response regulator (RR) play key roles in pathogenicity, but have not been comparatively studied for these oral bacterial pathogens.
    • Genomic Analysis of the Evolution of Phototrophy among Haloalkaliphilic Rhodobacterales.

      Kopejtka, Karel; Tomasch, Jürgen; Zeng, Yonghui; Tichý, Martin; Sorokin, Dimitry Y; Koblížek, Michal; Helmholtz Centre for infection research, Inhoffenstr.7,38124 Braunschweig, Germany. (2017-07-01)
      A characteristic feature of the order Rhodobacterales is the presence of a large number of photoautotrophic and photoheterotrophic species containing bacteriochlorophyll. Interestingly, these phototrophic species are phylogenetically mixed with chemotrophs. To better understand the origin of such variability, we sequenced the genomes of three closely related haloalkaliphilic species, differing in their phototrophic capacity and oxygen preference: the photoheterotrophic and facultatively anaerobic bacterium Rhodobaca barguzinensis, aerobic photoheterotroph Roseinatronobacter thiooxidans, and aerobic heterotrophic bacterium Natronohydrobacter thiooxidans. These three haloalcaliphilic species are phylogenetically related and share many common characteristics with the Rhodobacter species, forming together the Rhodobacter-Rhodobaca (RR) group. A comparative genomic analysis showed close homology of photosynthetic proteins and similarity in photosynthesis gene organization among the investigated phototrophic RR species. On the other hand, Rhodobaca barguzinensis and Roseinatronobacter thiooxidans lack an inorganic carbon fixation pathway and outer light-harvesting genes. This documents the reduction of their photosynthetic machinery towards a mostly photoheterotrophic lifestyle. Moreover, both phototrophic species contain 5-aminolevulinate synthase (encoded by the hemA gene) incorporated into their photosynthesis gene clusters, which seems to be a common feature of all aerobic anoxygenic phototrophic Alphaproteobacteria. Interestingly, the chrR-rpoE (sigma24) operon, which is part of singlet oxygen defense in phototrophic species, was found in the heterotrophic strain Natronohydrobacter thiooxidans. This suggests that this organism evolved from a photoheterotrophic ancestor through the loss of its photosynthesis genes. The overall evolution of phototrophy among the haloalkaliphilic members of the RR group is discussed.
    • Genomics and physiology of a marine flavobacterium encoding a proteorhodopsin and a xanthorhodopsin-like protein.

      Riedel, Thomas; Gómez-Consarnau, Laura; Tomasch, Jürgen; Martin, Madeleine; Jarek, Michael; González, José M; Spring, Stefan; Rohlfs, Meike; Brinkhoff, Thorsten; Cypionka, Heribert; Göker, Markus; Fiebig, Anne; Klein, Johannes; Goesmann, Alexander; Fuhrman, Jed A; Wagner-Döbler, Irene; Helmholtz-Centre for Infection Research, Braunschweig, Germany. Thomas.Riedel@helmholtz-hzi.de (2013)
      Proteorhodopsin (PR) photoheterotrophy in the marine flavobacterium Dokdonia sp. PRO95 has previously been investigated, showing no growth stimulation in the light at intermediate carbon concentrations. Here we report the genome sequence of strain PRO95 and compare it to two other PR encoding Dokdonia genomes: that of strain 4H-3-7-5 which shows the most similar genome, and that of strain MED134 which grows better in the light under oligotrophic conditions. Our genome analysis revealed that the PRO95 genome as well as the 4H-3-7-5 genome encode a protein related to xanthorhodopsins. The genomic environment and phylogenetic distribution of this gene suggest that it may have frequently been recruited by lateral gene transfer. Expression analyses by RT-PCR and direct mRNA-sequencing showed that both rhodopsins and the complete β-carotene pathway necessary for retinal production are transcribed in PRO95. Proton translocation measurements showed enhanced proton pump activity in response to light, supporting that one or both rhodopsins are functional. Genomic information and carbon source respiration data were used to develop a defined cultivation medium for PRO95, but reproducible growth always required small amounts of yeast extract. Although PRO95 contains and expresses two rhodopsin genes, light did not stimulate its growth as determined by cell numbers in a nutrient poor seawater medium that mimics its natural environment, confirming previous experiments at intermediate carbon concentrations. Starvation or stress conditions might be needed to observe the physiological effect of light induced energy acquisition.
    • The global impact of the delta subunit RpoE of the RNA polymerase on the proteome of Streptococcus mutans.

      Xue, Xiaoli; Li, Jinshan; Wang, Wei; Sztajer, Helena; Wagner-Döbler, Irene; Research Group Microbial Communication, Division of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. Xiaoli.Xue@helmholtz-hzi.de (2012-01)
      Transcriptional specificity in low-G+C Gram-positive bacteria is maintained by RpoE, the delta subunit of the RNA polymerase. Here, we studied the effect of RpoE at the proteome level in the human dental pathogen Streptococcus mutans by comparing the ΔrpoE mutant with the wild-type under five conditions: (0) exponential growth, (1) early stationary phase, (2) acid stress, (3) oxidative stress, and (4) combined acid and oxidative stress. A total of 280 cellular protein spots were reproducibly detected, of which 97 differentially expressed protein spots were identified by MALDI-TOF MS. Lack of RpoE caused downregulation of proteins for carbohydrate metabolism and energy production, including phosphoglucomutase (PGM), the phosphopentomutase DeoB and the pyruvate formate-lyase Pfl. The ΔrpoE mutant had extensive changes in the abundance of proteins involved in acid and oxidative tolerance and protein turnover, and of chaperones, at exponential phase in the absence of stress, suggesting a potential internal stress. In addition, the mutant had reduced amounts of proteins for adaptation responses, e.g. the multiple sugar transport and metabolism enzymes required for entering early stationary phase, and the proteins for stress-defence mechanisms and glycolysis under oxidative stress. Comparison of the proteome data with the corresponding transcriptome data suggested that the effects were the result of altered transcriptional and post-transcriptional regulation. The data are consistent with the reduced transcriptional specificity of the RNA polymerase in the ΔrpoE mutant, and suggest a general impact, but not a specific regulatory role, of RpoE in stress adaptation.
    • High-resolution taxonomic profiling of the subgingival microbiome for biomarker discovery and periodontitis diagnosis.

      Szafranski, Szymon P; Wos-Oxley, Melissa L; Vilchez-Vargas, Ramiro; Jáuregui, Ruy; Plumeier, Iris; Klawonn, Frank; Tomasch, Jürgen; Meisinger, Christa; Kühnisch, Jan; Sztajer, Helena; Pieper, Dietmar H; Wagner-Döbler, Irene; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2015-02)
      The oral microbiome plays a key role for caries, periodontitis, and systemic diseases. A method for rapid, high-resolution, robust taxonomic profiling of subgingival bacterial communities for early detection of periodontitis biomarkers would therefore be a useful tool for individualized medicine. Here, we used Illumina sequencing of the V1-V2 and V5-V6 hypervariable regions of the 16S rRNA gene. A sample stratification pipeline was developed in a pilot study of 19 individuals, 9 of whom had been diagnosed with chronic periodontitis. Five hundred twenty-three operational taxonomic units (OTUs) were obtained from the V1-V2 region and 432 from the V5-V6 region. Key periodontal pathogens like Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia could be identified at the species level with both primer sets. Principal coordinate analysis identified two outliers that were consistently independent of the hypervariable region and method of DNA extraction used. The linear discriminant analysis (LDA) effect size algorithm (LEfSe) identified 80 OTU-level biomarkers of periodontitis and 17 of health. Health- and periodontitis-related clusters of OTUs were identified using a connectivity analysis, and the results confirmed previous studies with several thousands of samples. A machine learning algorithm was developed which was trained on all but one sample and then predicted the diagnosis of the left-out sample (jackknife method). Using a combination of the 10 best biomarkers, 15 of 17 samples were correctly diagnosed. Training the algorithm on time-resolved community profiles might provide a highly sensitive tool to detect the onset of periodontitis.
    • Hoeflea phototrophica sp. nov., a novel marine aerobic alphaproteobacterium that forms bacteriochlorophyll a.

      Biebl, Hanno; Tindall, Brian J; Pukall, Rüdiger; Lünsdorf, Heinrich; Allgaier, Martin; Wagner-Döbler, Irene (2006-04-01)
      Within a collection of marine strains that were shown to contain the photosynthesis reaction-centre genes pufL and pufM, a novel group of alphaproteobacteria was found and was characterized phenotypically. The 16S rRNA gene sequence data suggested that the strains belonged to the order Rhizobiales and were closest (98.5 % sequence similarity) to the recently described species Hoeflea marina. The cells contained bacteriochlorophyll a and a carotenoid, presumably spheroidenone, in small to medium amounts. Cells of the novel strains were small rods and were motile by means of single polarly inserted flagella. Good growth occurred in complex media with 0.5-7.0 % sea salts, at 25-33 degrees C (optimum, 31 degrees C) and at pH values in the range 6-9. With the exception of acetate and malate, organic carbon sources tested supported poor growth or no growth at all. Growth factors were required; these were provided by small amounts of yeast extract, but not by standard vitamin solutions. Growth occurred under aerobic to microaerobic conditions, but not under anaerobic conditions, either in the dark or light. Nitrate was not reduced. Photosynthetic pigments were formed at low to medium salt concentrations, but not at the salt concentration of sea water (3.5 %). On the basis of smaller cell size, different substrate utilization profile and photosynthetic pigment content, the novel strains can be classified as representatives of a second species of Hoeflea, for which the name Hoeflea phototrophica sp. nov. is proposed. The type strain of Hoeflea phototrophica sp. nov. is DFL-43T (=DSM 17068T = NCIMB 14078T).
    • Horizontal operon transfer, plasmids, and the evolution of photosynthesis in Rhodobacteraceae

      Brinkmann, Henner; Göker, Markus; Koblížek, Michal; Wagner-Döbler, Irene; Petersen, Jörn; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany.
    • Identification of Genetic Modules Mediating the Jekyll and Hyde Interaction of Dinoroseobacter shibae with the Dinoflagellate Prorocentrum minimum.

      Wang, Hui; Tomasch, Jürgen; Michael, Victoria; Bhuju, Sabin; Jarek, Michael; Petersen, Jörn; Wagner-Döbler, Irene; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2015)
      The co-cultivation of the alphaproteobacterium Dinoroseobacter shibae with the dinoflagellate Prorocentrum minimum is characterized by a mutualistic phase followed by a pathogenic phase in which the bacterium kills aging algae. Thus it resembles the "Jekyll-and-Hyde" interaction that has been proposed for other algae and Roseobacter. Here, we identified key genetic components of this interaction. Analysis of the transcriptome of D. shibae in co-culture with P. minimum revealed growth phase dependent changes in the expression of quorum sensing, the CtrA phosphorelay, and flagella biosynthesis genes. Deletion of the histidine kinase gene cckA which is part of the CtrA phosphorelay or the flagella genes fliC or flgK resulted in complete lack of growth stimulation of P. minimum in co-culture with the D. shibae mutants. By contrast, pathogenicity was entirely dependent on one of the extrachromosomal elements of D. shibae, the 191 kb plasmid. The data show that flagella and the CtrA phosphorelay are required for establishing mutualism and prove a cell density dependent killing effect of D. shibae on P. minimum which is mediated by an unknown factor encoded on the 191 kb plasmid.
    • Identification, synthesis, and conformation of tri- and tetrathiacycloalkanes from marine bacteria.

      Sobik, Paul; Grunenberg, Jörg; Böröczky, Katalin; Laatsch, Hartmut; Wagner-Döbler, Irene; Schulz, Stefan (2007-05-11)
      Seven new cyclic natural polysulfides 1-7 were identified in extracts of two bacterial Cytophaga strains (CFB-phylum) isolated from biofilms from the North Sea. Their structures are based on mono- and dimeric-cyclization products of 2-methylpropane-1,2-dithiol 8, which was also present in the extract in trace amounts. The structures were deduced by analysis of their mass spectra and confirmed by synthesis. The 1H NMR spectra of some these compounds suggested a high flexibility of the trithiepane and tetrathiocane systems. Therefore, their conformation was further analyzed by DFT calculations and dynamic NMR spectroscopy. While thiepane 4 possesses a twist-chair lowest energy conformation, its isomers 2 and 3 adopt a chairlike conformation, as does the tetrathiocane 5. In contrast, tetrathiocane 6 favors again a twisted chair conformation.
    • Integrated analysis of gene expression and metabolic fluxes in PHA-producing Pseudomonas putida grown on glycerol.

      Beckers, Veronique; Poblete-Castro, Ignacio; Tomasch, Jürgen; Wittmann, Christoph; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
      Given its high surplus and low cost, glycerol has emerged as interesting carbon substrate for the synthesis of value-added chemicals. The soil bacterium Pseudomonas putida KT2440 can use glycerol to synthesize medium-chain-length poly(3-hydroxyalkanoates) (mcl-PHA), a class of biopolymers of industrial interest. Here, glycerol metabolism in P. putida KT2440 was studied on the level of gene expression (transcriptome) and metabolic fluxes (fluxome), using precisely adjusted chemostat cultures, growth kinetics and stoichiometry, to gain a systematic understanding of the underlying metabolic and regulatory network.
    • Iromycins from Streptomyces sp. and from synthesis: new inhibitors of the mitochondrial electron transport chain.

      Surup, Frank; Shojaei, Heydar; von Zezschwitz, Paultheo; Kunze, Brigitte; Grond, Stephanie; Institute of Organic and Biomolecular Chemistry, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany. (2008-02-15)
      Two new alpha-pyridone metabolites, iromycins E and F, were isolated from cultures of strain Streptomyces sp. Dra 17, thus expanding the recently discovered iromycin family. The inhibitory potential on the mitochondrial respiratory chain was examined and revealed that iromycin metabolites block NADH oxidation in beef heart submitochondrial particles with different efficacy, yet remarkably show only very low cytotoxicity. Difference spectroscopic studies indicated that iromycins inhibit the electron transport at the site of complex I (NADH-ubiquinone oxidoreductase). Derivatives of the natural products were semisynthetically prepared and provided detailed insights into structure-activity relationships. Drawn from these results, there are strong similarities with the piericidins, which are among the most potent complex I inhibitors of the mitochondrial electron transport chain. Furthermore, total synthesis afforded new analogues, and the non-natural iromycin S (IC50 = 58 ng/mL) emerged as the most active compound, thus opening avenues of future studies with the iromycins as new valuable biochemical tools.