• Bioactive Compounds Produced by Hypoxylon fragiforme against Staphylococcus aureus Biofilms.

      Yuyama, Kamila Tomoko; Chepkirui, Clara; Wendt, Lucile; Fortkamp, Diana; Stadler, Marc; Abraham, Wolf-Rainer; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-12-12)
      Treating infections organized in biofilms is a challenge due to the resistance of the pathogens against antibiotics and host immune cells. Many fungi grow in a wet environment, favorable for the growth of bacterial biofilms, and we speculated that fungi possess some strategies to control these bacterial biofilms. A fungus identified as Hypoxylon fragiforme, was collected in the Harz Mountains, Germany, and its mycelial culture was fermented in different culture media for 67 days to test its biological potential against bacterial biofilms. Sclerin, sclerin diacid and its 3-methyl monoester (methyl 1-(5-hydroxy-6-carboxylic-2,3,4-trimethylphenyl) propionate) are here described for the first time from this fungus. Sclerin and its diacid interfered with the biofilm formation of the pathogen Staphylococcus aureus, inhibiting 86% and 80% of the biofilm at 256 μg mL-1, respectively, but not killing the bacterium. Interestingly, the monomethylester of sclerin diacid was inactive. Although these compounds did not possess any activity against a pre-formed biofilm, they prevented its formation at subtoxic concentrations. Furthermore, sclerin and its diacid displayed a high specificity against Staphylococcus aureus, indicating a good strategy against pathogenic biofilms when combined with antibiotics.
    • Brevundimonas vancanneytii sp. nov., isolated from blood of a patient with endocarditis.

      Estrela, Andréia B; Abraham, Wolf-Rainer; Helmholtz Center for Infection Research, Chemical Microbiology, Inhoffenstrasse 7, 38124 Braunschweig, Germany. (2010-09)
      A Gram-negative, rod-shaped, non-spore-forming bacterial strain, designated LMG 2337(T), was isolated from the blood of a patient with endocarditis and characterized. The strain was affiliated with the alphaproteobacterial genus Brevundimonas, with Brevundimonas diminuta LMG 2089(T) (98.3 % 16S rRNA gene sequence similarity) and Brevundimonas terrae KSL-145(T) (97.5 %) as its closest relatives. This affiliation was supported by chemotaxonomic data: the G+C content was 66.3 mol %, the major polar lipids were phosphatidyl diacylglycerol, sulfoquinovosyl diacylglycerol and phosphatidyl glucopyranosyl diacylglycerol and the major fatty acids were summed feature 7 (one or more of C(18 : 1)ω 7c, C(18 : 1)ω 9t and C(18 : 1)ω 12t) and C(16 : 0). Strain LMG 2337(T) displayed an unusually broad substrate spectrum. The results from DNA-DNA hybridization and physiological and biochemical tests allowed the genotypic and phenotypic differentiation of strain LMG 2337(T) from all of the type strains of hitherto-described Brevundimonas species. The strain therefore represents a novel species, for which the name Brevundimonas vancanneytii sp. nov. is proposed, with type strain LMG 2337(T) (=CCUG 1797(T) =ATCC 14736(T)).
    • Cauliform bacteria lacking phospholipids from an abyssal hydrothermal vent: proposal of Glycocaulis abyssi gen. nov., sp. nov., belonging to the family Hyphomonadaceae.

      Abraham, Wolf-Rainer; Lünsdorf, Heinrich; Vancanneyt, Marc; Smit, John; Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany. wolf-rainer.abraham@helmholtz-hzi.de (2013-06)
      Cauliform bacteria are prosthecate bacteria often specialized for oligotrophic environments. A polyphasic approach, comprising 16S rRNA gene sequencing, lipid analysis and salt tolerance characterizations, was used to clarify the taxonomy of one isolate, strain MCS 33(T), obtained from above the hot water plume of a deep-sea hydrothermal vent near Vancouver island, Canada. Cells contained no detectable phospholipids or sulpholipids, but did contain 1,2-di-O-acyl-3-O-α-D-glucopyranosylglycerol, 1,2-di-O-acyl-3-O-α-D-glucopyranuronosylglycerol and the novel lipid 1,2-di-O-acyl-3-[O-α-D-glucopyranuronosyl]glycerol-6'-N-glycine. It is assumed that the various glucoronosyl lipids are replacing, at least partially, the phospholipids in their various tasks in the cell cycle. The G+C content of the genomic DNA of strain MCS 33(T) was 62.8 mol%, and Q10 was the predominant respiratory ubiquinone. The 16S rRNA gene sequence of this chemoheterotrophic, aerobic, moderately halophilic strain showed only a low similarity of 94.4% to that of Oceanicaulis alexandrii C116-18(T), and both strains also differed based on their lipids. Although the novel strain was isolated from seawater sampled near a hydrothermal vent, its optimum temperature for growth was 30 °C. The main cellular fatty acids were C18:1ω7c, C18:0 and the unknown fatty acid ECL 11.798, and the main hydroxy fatty acid was C12:0 3-OH. The strain is proposed to represent a novel species of a new genus, Glycocaulis abyssi gen. nov., sp. nov. The type strain of the type species is MCS 33(T) (=LMG 27140(T)=CCUG 62981(T)).
    • Chemische Funktionalisierung und Materialoptimierung dentaler Implantat-Abutments zur Reduktion der oralen Biofilmbildung

      Stiesch, Meike; Menzel, Henning; Abraham, Wolf-Rainer; Müller, Peter Paul; Dempwolf, Wiebke; Pfaffenroth, Cornelia; Kohorst, Phillip; Winkel, Andreas; Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124, Braunschweig, Germany. (Druckerei der Medizinischen Hochschule, 2012-07-06)
    • cis-2-Alkenoic acids as promising drugs for the control of biofilm infections.

      Yuyama, Kamila Tomoko; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-05-06)
      Microbes attached to surfaces and form biofilms where they are difficult to eradicate. Here they are embedded in a complex matrix of polymers and are much less sensitive against antibiotics or the immune system.
    • Combining Biofilm-Controlling Compounds and Antibiotics as a Promising New Way to Control Biofilm Infections

      Estrela, Andréia Bergamo; Abraham, Wolf-Rainer; HelmholtzCenter for Infection Research, Inhoffenstr. 7, 38124 Braunschweig, Germany (2010-05-21)
    • Combining Biofilm-Controlling Compounds and Antibiotics as a Promising New Way to Control Biofilm Infections.

      Estrela, Andréia Bergamo; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2010-05-11)
      Many bacteria grow on surfaces forming biofilms. In this structure, they are well protected and often high dosages of antibiotics cannot clear infectious biofilms. The formation and stabilization of biofilms are mediated by diffusible autoinducers (e.g. N-acyl homoserine lactones, small peptides, furanosyl borate diester). Metabolites interfering with this process have been identified in plants, animals and microbes, and synthetic analogues are known. Additionally, this seems to be not the only way to control biofilms. Enzymes capable of cleaving essential components of the biofilm matrix, e.g. polysaccharides or extracellular DNA, and thus weakening the biofilm architecture have been identified. Bacteria also have mechanisms to dissolve their biofilms and return to planktonic lifestyle. Only a few compounds responsible for the signalling of these processes are known, but they may open a completely novel line of biofilm control. All these approaches lead to the destruction of the biofilm but not the killing of the pathogens. Therefore, a combination of biofilm-destroying compounds and antibiotics to handle biofilm infections is proposed. In this article, different approaches to combine biofilm-controlling compounds and antibiotics to fight biofilm infections are discussed, as well as the balance between biofilm formation and virulence.
    • Community-based degradation of 4-chorosalicylate tracked on the single cell level.

      Pawelczyk, Sonja; Abraham, Wolf-Rainer; Harms, Hauke; Müller, Susann; University of Oxford, Department of Biochemistry, South Parks Road, OX1 3QU, Oxford, UK. (2008-09)
      4-Chlorosalicylate (4-CS) can be degraded completely by a bacterial consortium consisting of Pseudomonas reinekei (MT1), Achromobacter spanius (MT3) and Pseudomonas veronii (MT4). The fourth species Wautersiella falsenii (MT2) is thought to act as a 'necrotizer' of the community. Single cell approaches were used to follow every species' degradation activity within the community by assuming that growth and proliferation are activity markers for the utilization of 4-CS and its degradation pathway intermediates as carbon and energy sources. A primary/secondary antibody staining technique for species differentiation was applied and a species-resolved determination of proliferation activity by flow cytometry undertaken. Degradation was followed by quantifying 4-CS and the resulting intermediates by HPLC. A good correlation of HPLC bulk data with the proliferation activity states of every species within the community was found. It was also assumed that reduced activity of strain MT4 and increased proliferation of strain MT2 might have caused an observed breakdown of the consortium grown in the bioreactor. The double staining technique provided the chance to follow bacterial cell states and their roles in mixed cultures without applying labelled substrates. It is therefore in line with single cell techniques already successfully applied in biotechnology for developing strategies to optimize microbially catalyzed production processes.
    • Coprinuslactone protects the edible mushroom Coprinus comatus against biofilm infections by blocking both quorum-sensing and MurA.

      de Carvalho, Maira P; Gulotta, Giuseppe; do Amaral, Matheus W; Lünsdorf, Heinrich; Sasse, Florenz; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-10-03)
      Pathogens embedded in biofilms are involved in many infections and are very difficult to treat with antibiotics because of higher resistance compared to planktonic cells. Therefore, new approaches for their control are urgently needed. One way to search for biofilm dispersing compounds is to look at defense strategies of organisms exposed to wet environments, which makes them prone to biofilm infections. It is reasonable to assume that mushrooms have developed mechanisms to control biofilms on their sporocarps (fruiting bodies). A preliminary screening for biofilms on sporocarps revealed several species with few or no bacteria on their sporocarps. From the edible mushroom Coprinus comatus where no bacteria on the sporocarp could be detected (3R,4S)-2-methylene-3,4-dihydroxypentanoic acid 1,4-lactone, named coprinuslactone, was isolated. Coprinuslactone interfered with quorum-sensing and dispersed biofilms of Pseudomonas aeruginosa, where it also reduced the formation of the pathogenicity factors pyocyanin and rhamnolipid B. Coprinuslactone also damaged Staphylococcus aureus cells in biofilms at subtoxic concentrations. Furthermore, it inhibited UDP-N-acetylglucosamine enolpyruvyl transferase (MurA), essential for bacterial cell wall synthesis. These two modes of action ensure the inhibition of a broad spectrum of pathogens on the fruiting body but may also be useful for future clinical applications. This article is protected by copyright. All rights reserved.
    • Cytochalasans Act as Inhibitors of Biofilm Formation of Staphylococcus Aureus.

      Yuyama, Kamila Tomoko; Wendt, Lucile; Surup, Frank; Kretz, Robin; Chepkirui, Clara; Wittstein, Kathrin; Boonlarppradab, Chollaratt; Wongkanoun, Sarunyou; Luangsa-Ard, Jennifer; Stadler, Marc; et al. (MPDI, 2018-10-30)
      During the course of our ongoing work to discover new inhibitors of biofilm formation of Staphylococcus aureus from fungal sources, we observed biofilm inhibition by cytochalasans isolated from cultures of the ascomycete Hypoxylon fragiforme for the first time. Two new compounds were purified by a bioassay-guided fractionation procedure; their structures were elucidated subsequently by nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS). This unexpected finding prompted us to test further cytochalasans from other fungi and from commercial sources for comparison. Out of 21 cytochalasans, 13 showed significant inhibition of Staphylococcus aureus biofilm formation at subtoxic levels. These findings indicate the potential of cytochalasans as biofilm inhibitors for the first time, also because the minimum inhibitory concentrations (MIC) are independent of the anti-biofilm activities. However, cytochalasans are known to be inhibitors of actin, making some of them very toxic for eukaryotic cells. Since the chemical structures of the tested compounds were rather diverse, the inclusion of additional derivatives, as well as the evaluation of their selectivity against mammalian cells vs. the bacterium, will be necessary as next step in order to develop structure-activity relationships and identify the optimal candidates for development of an anti-biofilm agent. View Full-Text
    • Different implants have different biofilm communities-lessons for implant optimization

      Abraham, Wolf-Rainer; Dept. of chemical microbiology, Helmholtz Centre for infection research, D-38124 Braunschweig, Germany. (Walter de Gruyter GmbH & Co. KG, 2014-12-09)
    • Dipeptide cis-cyclo(Leucyl-Tyrosyl) produced by sponge associated Penicillium sp. F37 inhibits biofilm formation of the pathogenic Staphylococcus epidermidis.

      Scopel, Marina; Abraham, Wolf-Rainer; Henriques, Amélia T; Macedo, Alexandre J; Faculdade de Farmácia, Departamento de Produção de Matéria-Prima, Universidade Federal do Rio Grande do Sul, Av. Ipiranga, 2752, 90610-000 Porto Alegre, Brazil. (2013-02-01)
      Infections associated to microbial biofilms are involved in 80% of human infections and became a challenge concerning public health. Infections related to Staphylococcus epidermidis biofilms are presently commonly associated to medical devices, increasing treatment costs for this type of infection. Alternatives to eliminate this kind of disease have been employed in screening programs using diverse marine-derived fungi source of bioactive compounds capable to combat biofilm formation. In this work was isolated the dipeptide cis-cyclo(Leucyl-Tyrosyl) from a sponge associated Penicillium sp. possessing a remarkable inhibition up to 85% of biofilm formation without interfering with bacterial growth, confirmed by scanning electron microscopy. This is the first demonstration that cis-cyclo(Leucyl-Tyrosyl) is able to specifically inhibit biofilm formation adding another aspect to the broad spectrum of bioactivities of cyclic dipeptides.
    • Diversity and Activity of Bacterial Biofilm Communities Growing on Hexachlorocyclohexane

      Gebreil, Ahmed Shawky; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-08-03)
    • 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.
    • Fumitremorgins and Relatives - from Tremorgenic Compounds to Valuable Anti-Cancer Drugs.

      Abraham, Wolf-Rainer; Hemholtz Centre for infection research, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-07-24)
      Fumitremorgins are mycotoxins but can also inhibit cancer cells and reverse their drug resistance.
    • Fungal Metabolites for the Control of Biofilm Infections

      Estrela, Andréia; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-08-12)
    • Going beyond the Control of Quorum-Sensing to Combat Biofilm Infections.

      Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
      Most bacteria attach to surfaces where they form a biofilm, cells embedded in a complex matrix of polymers. Cells in biofilms are much better protected against noxious agents than free-living cells. As a consequence it is very difficult to control pathogens with antibiotics in biofilm infections and novel targets are urgently needed. One approach aims at the communication between cells to form and to maintain a biofilm, a process called quorum-sensing. Water soluble small-sized molecules mediate this process and a number of antagonists of these compounds have been found. In this review natural compounds and synthetic drugs which do not interfere with the classical quorum-sensing compounds are discussed. For some of these compounds the targets are still not known, but others interfere with the formation of exopolysaccharides, virulence factors, or cell wall synthesis or they start an internal program of biofilm dispersal. Some of their targets are more conserved among pathogens than the receptors for quorum sensing autoinducers mediating quorum-sensing, enabling a broader application of the drug. The broad spectrum of mechanisms, the diversity of bioactive compounds, their activity against several targets, and the conservation of some targets among bacterial pathogens are promising aspects for several clinical applications of this type of biofilm-controlling compound in the future.
    • Human β-Defensin 2 Induces Extracellular Accumulation of Adenosine in Escherichia coli.

      Estrela, Andreia Bergamo; Rohde, Manfred; Gutierrez, Maximiliano Gabriel; Molinari, Gabriella; Abraham, Wolf-Rainer; Chemical Microbiology. (2013-09)
      Human β-defensins are host defense peptides performing antimicrobial as well as immunomodulatory functions. The present study investigated whether treatment of Escherichia coli with human β-defensin 2 could generate extracellular molecules of relevance for immune regulation. Mass spectrometry analysis of bacterial supernatants detected the accumulation of purine nucleosides triggered by β-defensin 2 treatment. Other cationic antimicrobial peptides tested presented variable outcomes with regard to extracellular adenosine accumulation; human β-defensin 2 was the most efficient at inducing this response. Structural and biochemical evidence indicated that a mechanism other than plain lysis was involved in the observed phenomenon. By use of isotope ((13)C) labeling, extracellular adenosine was found to be derived from preexistent RNA, and a direct interaction between the peptide and bacterial nucleic acid was documented for the first time for β-defensin 2. Taken together, the data suggest that defensin activity on a bacterial target may alter local levels of adenosine, a well-known immunomodulator influencing inflammatory processes.
    • Kinetics of carbon sharing in a bacterial consortium revealed by combining stable isotope probing with fluorescence-activated cell sorting.

      Pawelczyk, S; Bumann, D; Abraham, Wolf-Rainer; Helmholtz Center for Infection Research, Chemical Microbiology, Braunschweig, Germany. (2011-02-07)
      Aims:  To determine the kinetics of substrate fluxes in a microbial community in order to elucidate the roles of the community members. Methods and Results:  The kinetics of substrate sharing in a bacterial consortium were measured by a new analytical approach combining immunostaining, stable isotope probing and fluorescence-activated cell sorting (FACS). The bacterial consortium, consisting of four strains and growing on 4-chlorosalicylate (4-CS), was pulse-dosed with the degradation intermediate [U-(13) C]-4-chlorocatechol (4-CC). Cells were stained with strain-specific antibodies sorted by FACS and the (13) C-incorporation into fatty acids of the two most abundant members of the community was determined by isotope ratio mass spectrometry. From the two most abundant strains, the primary degrader Pseudomonas reinekei MT1 incorporated the labelled substrate faster than strain Achromobacter spanius MT3 but the maximal incorporation in strain MT3 was almost three times higher than in MT1. Conclusions:  It has been reported that strain MT1 produces 4-CC as an intermediate but has a lower LD(50) for it than strain MT3; therefore, MT3 still degrades 4-CC when the concentrations of 4-CC are already too toxic, even lethal, for MT1. By degrading 4-CC, produced by MT1, MT3 protects the entire community against this toxin. The higher affinity but lower tolerance of strain MT1 for 4-chlorocatechol compared to strain MT3 explains the complementary function these two strains have in the consortium adding exceptional stability to the entire community. Significance and Impact of the Study:  The novel approach can reveal carbon fluxes in microbial communities generating quantitative data for systems biology of the microbial community.