VAAM-Jahrestagung 2012 18.–21. März in Tübingen

52ISV01Die verborgene Welt der Bakterien und ihre Bedeutung fürdas Leben auf der ErdeK.-H. SchleiferTechnische Universität München, Mikrobiologie, München, GermanyBei Bakterien denken die meisten Menschen an Krankheitserreger. Dochdie überwiegende Mehrheit dieser Organismen ist harmlos oder sogarnützlich. Sie spielen eine wichtige Rolle bei der Herstellung fermentierterLebensmittel oder in der weißen Biotechnologie. Die zellkernlosenProkaryoten (Bakterien + Archaeen) sind jedoch noch aus anderenGründen sehr wichtig. Sie kommen in ungeheuer großen Zahlen vor undmachen ca. 50% der globalen Biomasse aus. Leider ist bisher nur einBruchteil von ihnen bekannt, da sie als Reinkultur nicht zugänglich sind.Durch genotypische Methoden, insbesondere durch vergleichendeSequenzanalyse der 16S-rRNS Gene ist es allerdings möglich, dieOrganismen auch ohne vorherige Kultivierung zu identifizieren. Mit Hilfemaßgeschneiderter, fluoreszenzmarkierter Oligonukleotidsonden, die ankomplementäre Sequenzen der 16S-rRNS binden, lassen sich dieOrganismen auch in situ nachweisen und identifizieren. Dies soll anhandverschiedener Beispiele belegt werden.Die Prokaryoten sind die Wegbereiter der Biosphäre. Für mindestens 2Milliarden Jahre waren sie die einzigen Lebewesen auf unserem Planeten.Sie waren an der Entstehung der höheren Lebewesen (Eukaryoten)beteiligt, und die Cyanobakterien sorgten für den nötigen Sauerstoff aufder Erde. Der Nährstoffkreislauf, insbesondere Stickstoff-und Schwefelkreislauf,wäre ohne die Prokaryoten unvollständig. Überdies zeichnen siesich durch einzigartige Mechanismen der Energiegewinnung aus, und siesetzen auch die Grenzen des Lebens fest. Sie wachsen überall, wo nochflüssiges Wassers vorkommt.Die Bakterien spielen auch eine besondere Rolle in der Evolution undÖkologie der Eukaryoten. Sie können als Kommensalen, Endo- oderEktosymbionten vorkommen. Dies soll an verschiedenen Beispielengezeigt werden.Bakterien und Archaeen sind durch ihre vielfältigen Aktivitäten wichtigfür Umwelt und Klima. Sie sind entscheidend an Aufbau und Erhalt derBiosphäre beteiligt. Ohne sie wäre die Mineralisierung organischer Stoffeunvollständig und ohne sie gäbe es auch nicht die typischen Eukaryoten.Der Vorläufer der heutigen Mitochondrien, den Energiekraftwerken dereukaryotischen Zellen, gehört zu den Alpha-Proteobakterien und dieChloroplasten, in denen die Photosynthese stattfindet, stammen vonCyanobakterien ab. All dies spricht dafür, dass es ohne Bakterien keinLeben auf unserem Planeten gäbe.ISV02From microorganisms to the atmosphere: flooded soils and themethane cycleR. ConradMax-Planck-Institut für terrestrische Mikrobiologie, Biogeochemie,Marburg, GermanyFlooded soils such as rice fields and wetlands are the most importantsource for the greenhouse gas methane. Rice fields, in particular, serve asmodel for studying the role of the structure of anaerobic microbialcommunities for ecosystem functioning and the partitioning of carbon fluxalong different paths of degradation of organic matter to methane. Floodedsoils are relatively rapidly depleted of oxygen and other oxidants such asferric iron and sulfate. Then, organic matter degradation results in theproduction methane. Methane is eventually produced from different typesof organic matter, mainly from plant litter, root exudates, and soil organicmatter. Methane production is achieved by a community consisting ofhydrolytic, fermenting and methanogenic microorganisms. Acetate andhydrogen (plus CO 2) are the two most important fermentation productsthat are used as methanogenic substrates to different extent. The transportof CH 4 to the atmosphere is mainly partitioned between transport throughthe aerenchyma system of plants, gas ebullition and diffusion. Transportthrough oxygenated zones such as the surface soil or the rhizosphereresults in oxidation of a substantial percentage of methane bymethanotrophic bacteria thus attenuating the methane flux into theatmosphere. Tracer experiments (e.g. using stable carbon isotopes) areuseful for quantifying the partitioning of carbon flux along different pathsand for elucidating the active microbial groups involved in carbontransformation.ISV03Physiology, mechanisms and habitats of microbial Fe(II) oxidationA. KapplerUniversity of Tübingen, Geomicrobiology, Center for AppliedGeosciences, Tübingen, GermanyThe two most important redox states of iron in the environment are Fe(II)[ferrous iron] and Fe(III) [ferric iron]. Dissolved Fe(II), relatively solubleFe(II) minerals and poorly soluble Fe(III) minerals are abundant in pHneutralsoils and sediments. Redox transformation of iron leading either todissolution, transformation or precipitation of iron minerals is used bymany microorganisms to produce energy and to grow. Oxidation ofdissolved ferrous iron [Fe(II)] at neutral pH can be catalyzed byacidophilic aerobic and neutrophilic microaerophilic, nitrate-reducing andeven phototrophic microorganisms. This contribution will present thecurrent knowledge and new results regarding mechanisms, physiology,ecology and environmental implications of microbial Fe(II) oxidation.Special focus will be on microaerophilic Fe(II)-oxidizing bacteria thatthrive in gradients of ferrous iron and oxygen (e.g. at the surface of riceroots in paddy soil), phototrophic Fe(II)-oxidizing autotrophs living insurface near environments such as littoral sediments, and finally on nitratereducingbacteria oxidizing Fe(II) in soils and sediments.ISV04Assembly and function of archaeal surface structuresS.-V. AlbersMax-Planck-Institut für terrestrische Mikrobiologie, Marburg, GermanyArchaea, the third domain of life, possess a variety of surface structuressuch as pili and flagella. These structures have in common that they arecomposed of subunits that are found in bacterial type IV pili which amongothers are involved in bacterial pathogenesis. The archaeal pili and flagellasystems appear to be much simpler than their bacterial counterparts and aretherefore well suited model systems to understand the mechanistic of theassembly process.The thermoacidophilic archaeon Sulfolobus acidocaldariusexhibits three different surface appendages, (i) flagella, (ii) thin pili, and (iii) UVlight induced pili. In Sulfolobus the flagellum is mainly involved in adhesion andsurface motility, which seems to be inhibited by the thin pili. The UV inducedpili initiate cell aggregation after DNA damage and subsequent DNA repair byconjugation. Next to the physiological function of these surface structures ourunderstanding of their assembly will be discussed.ISV05Current views on the role as well as the fate of host cellsduring infectionThomas F. Meyer and coworkersDepartment of Molecular Biology, Max Planck Institute for Infection Biology,Berlin, GermanyInfectious disease research has led us to the realization that the initiationand progression of infection are critically dependent on both pathogen andhost determinants. Microbial virulence factors have been studied in greatdetail over the past decades; however, the role of host determinants as thecounterparts of pathogen virulence factors and signal transductionelements has been less intensely pursued. With the discovery of RNAi, anextremely useful tool has become available that facilitates the assessmentof host-cell determinants and their role in infection at the genome-widelevel. Here, I present two examples of global host-cell function analysis,addressing influenza virus and Chlamydia infections (1,2), and discuss theimplications for the development of a novel class of therapeutic drugs aswell as for our future understanding of host susceptibility to infection andmorbidity/mortality determinants.Host cells are not merely vehicles for pathogen replication; it appears hostcells are also subject to genetic and epigenetic modifications duringinfection, and are therefore capable of acquiring heritable features that mayunderlie pathological sequelae, including cancer. The gastric pathogenHelicobacter pylori is the paradigm of a cancer-inducing bacterium (3).We, and others, can show that H. pylori and other bacterial pathogens arecapable of causing genetic and epigenetic lesions in infected cells (4).However, DNA damage alone does not seem to be sufficient in itself forcarcinogenesis. Other features such as persistence of infection andmitogenic stimuli are likely cofactors (5).1. Karlas, A., N.Machuy, Y.Shin, K.-P.Pleissner, A.Artarini, D.Heuer, D.Becker, H.Khalil, L.A.Ogilvie,S.Hess, A.P.Mäurer, E.Müller, T.Wolff, T.Rudel, and T.F.Meyer. 2010. Genome-wide RNAi screenidentifies human host factors crucial for influenza virus replication. Nature 463:818-822.2. Gurumurthy, R.K., A.P.Mäurer, N.Machuy, S.Hess, K.P.Pleissner, J.Schuchhardt, T.Rudel, andT.F.Meyer. 2010. A loss-of-function screen reveals Ras- and Raf-independent MEK-ERK signaling duringChlamydia trachomatis infection. Science Signaling 3:ra21.3. Bauer, B., and T.F.Meyer. 2011. The human gastric pathogen Helicobacter pylori and its association withgastric cancer and ulcer disease. Ulcers. doi:10.1155/2011/3401574. Fassi Fehri, L., C.Rechner, S.Janssen, T.N.Mak, C.Holland, S.Bartfeld, H.Bruggemann, and T.F.Meyer.2009. Helicobacter pylori-induced modification of the histone H3 phosphorylation status in gastric epithelialcells reflects its impact on cell cycle regulation. Epigenetics. 4:577-586.5. Kessler, M., J.Zielecki, O.Thieck, H.J.Mollenkopf, C.Fotopoulou, and T.F.Meyer. 2011. ChlamydiaTrachomatis Disturbs Epithelial Tissue Homeostasis in Fallopian Tubes via Paracrine Wnt Signaling. Am. JPathol..180:186-198.ISV06No abstract submitted!BIOspektrum | Tagungsband 2012