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

233SSP020Hot trehalose: A report about the unusual bifunctional TPSPpathway in Thermoproteus tenaxA. Hagemann* 1 , M. Zaparty 2 , C. Bräsen 1 , B. Siebers 11 University of Duisburg-Essen, Biofilm Centre, Molecular Enzymetechnologyand Biochemistry, Essen, Germany2 University of Regensburg, Institute for Molecular and Cellular Anatomy,Regensburg, GermanyThe widespread non-reducing disaccharide trehalose, consisting of two a-1,1 linked glycosyl-glucose molecules, is known to function as compatiblesolute in Eucarya and Bacteria, protecting the cell against a wide range ofdifferent stress conditions [1]. Trehalose has been identified in Archaea,but its function is still unknown.The (OtsA/OtsB) TPS/TPP pathway via trehalose-6-phosphate synthase(TPS) and trehalose-6-phosphate phosphatase (TPP) is the most commonpathway for trehalose synthesis. UDP (ADP-) glucose and glucose-6-phosphate are transformed into trehalose-6-phosphate by TPS andsubsequently dephosphorylated by TPP forming trehalose and P i [2]. In thegenome of the hyperthermophilic Crenarchaeon Thermoproteus tenax anoperon comprising a gene coding for a trehalose-6-phosphatesynthase/phosphatase (tpsp), with a C-terminal TPS- and N-terminal TPPdomainwas identified [3]. This operon also harbors a putative glycosyltransferase (gt) and a putative small conductive mechanosensitve channel(msc). The two-domain TPSP structure has already been described forplants (e.g. Selaginella leptophylla, Arabidopsis thaliana) and forSaccharomyces cerevisiae, but these TPSPs only possesses one activity,either TPS or TPP. Only recently a bifunctional TPSP activity has beenreported from Cytophaga hutchinsonii [4]. For the Archaeon T. tenax,biochemical studies of the recombinant protein revealed a TPSP with fullTPP activity and only in the presence of GT bifunctional TPSP activitywas observed. In our current model, we suggest that GT activates TPSP bycomplex formation. The MCS might function as the emergency valvewhich allows the maintenance of the cell turgor in order to respond toenvironmental cues (e.g. osmotic stress).[1] Elbeinet al., Glycobiology,13, 4 (2003)[2] Avonce,et al., BMC Evolutionary Biology.6(2006), p.109[3] Siebers, B.et al., J. Bacteriol.186(2004), p.2179-2194[4] Avonce, N.et al., Mol. Biol. Evol.27(2) (2010), p.359-369.SSP021Evolutionary stabilisation of bacterial cooperation by switchesbetween microcolonial and planktonic life styleB.A. Hense* 1 , A. Mund 1,2 , C. Kuttler 2 , M. Ehler 11 Helmholtz Zentrum München, Institute of Biomathematics and Biometry,Neuherberg, Germany2 Technische Universität München, Centre for Mathematical Science ,Munich, GermanyMechanisms ensuring evolutionary stability of bacterial cooperation arenot well understood. Bacterial autoinducer (AI) signals, i.e., diffusiblemolecules released by bacterial cells, enable a cooperative and coordinatedgene expression on population level [1]. This behaviour has been describedas quorum sensing or efficiency sensing. Cheater mutants save costs by notproducing the signal molecule or by avoiding the AI regulated cooperativephenotype expression. Therefore, they should outcompete cooperativecells. It has been proposed that kin selection mechanisms withinmicrocolonies, grown from common ancestors and thus composed ofclosely related cells, may promote the stability of AI systems. As AIsystems have also been described in plankton, and many bacteria speciesswitch between colonial and planktonic life style, a natural question arises:Can life style changes evolutionary stabilize AI functionality in plankton?As a first approach, we analyze this theoretically within a mathematicalmodel. We assume costly AI production, an AI regulated costly phenotypeexpression (as e.g. exoenzyme production), phenotype dependent logisticgrowth of the colonies and plankton, stochastic changes betweenmicrocolonial and planktonic life styles, cell as well as colony death, andmutation from wildtype to AI resp. exoenzyme deficient mutants. Firstresults indicate that life style switches can have stabilizing effects thatsupport an equilibrium between wildtype and cheater cells. The fraction ofcheater in the stationary state depends, among others, on the exchange ratebetween microcolonies and plankton as well as the colony death rate.[1] Hense et al. (2007) Does efficiency sensing unify diffusion and quorum sensing? Nat. Rev.Microbiol. 5: 230-239SSP022Fatty acid-independent adaptation of bacterial membranes tocold temperaturesJ. Derichs*, A. LipskiRheinische Friedrich-Wilhelms-Universität, Lebensmittelmikrobiologieund -hygiene, Bonn, GermanyThe adaptation of microorganisms to low temperatures is one of the mostimportant adaptations to extreme conditions because cold environmentsrepresent the majority of the biosphere on earth. Furthermore,psychrotolerant and psychrophilic microorganisms are of special interest inthe food industry with respect to food protection, safety and quality.One of the most significant adaptations of microorganisms to coldtemperatures is the control of cell membrane fluidity. Membrane fluidity isusually controlled by adaptations of the fatty acid profiles. However,during the last years we analyzed psychrotolerant bacterial isolates fromdifferent sources, Arctic and Antarctic soil samples, chilled food samplesand refrigerators, which show no or unexpected adaptations of their fattyacid profiles when grown under low temperatures. For these isolates weexpect other mechanisms involved in the modulation of membranefluidity.In this study we focused on the alteration of the cell quinone content asmechanism of membrane adaptation. We hypothesize that increase ofquinone concentration may result in an increase of the disorder ofmembrane fatty acid acyl chains disorder analogue to other lipophilicmembrane fluidizers. Therefore, quinones may be an alternative to fattyacid related effects like increase of monounsaturated fatty acids. Weanalysed several psychrotolerant bacterial strains for changes of their fattyacid profiles and quinone content when grown under differenttemperatures. For most strains we found a decrease in the quinone contentunder low temperature conditions. However, some strains of theBacillaceae showed increase of their quinone content under lowtemperature growth conditions in accord with our working hypothesis.From there, we hypothesize that for some bacterial taxa quinones play arole in the adaptation to cold temperatures and in the control of cellmembrane fluidity.SSP023Essential oils show specific inhibiting effects on biofilmformation by bacteriaS. Szczepanski*, A. LipskiRheinische Friedrich-Wilhelms-Universität, LebensmittelmikrobiologieundHygiene, Bonn, GermanyThe use of essential oils as food preservatives gets more and moreinteresting in the food processing industry. We analysed the inhibitingeffects of thyme, oregano and cinnamon essential oil on biofilm formationby strains of the genus Acinetobacter, Sphingomonas andStenotrophomonas. These biofilm forming test strains were isolated fromauthentic biofilms in the food industry during a previous study.Minimal inhibitory concentrations (MIC´s) for growth and biofilm formingactivity were tested in a 96-well microtiter plate assay. Biofilm formingactivity was tested based on a crystal violet assay. For some strainsinhibition of growth and inhibition of the biofilm formation by theessential oils are initiated at the same concentration. However, for strainsof the genus Acinetobacter and Sphingomonas we found an inhibitingeffect of essential oils on biofilm formation considerably below the MICfor growth of these strains. Thyme oil is capable to inhibit the developmentof a biofilm at low concentrations up to 0,002 %. This natural substanceseems to be the most efficient specific inhibitor compared with the othertested essential oils against the biofilm formation of all tested isolates.Controls showed that the detergent used, Tween 20, was not responsiblefor this effect. The same tests were carried out with the main componentsof the essential oils. Fluorescence microscopy was performed to visualizethe structural change of the biofilm after application of sublethalconcentrations of essential oils.The effective concentration of the natural substances was dependent on thetype of essential oil. The strains showed different sensitivity depending onthe oil.SSP024Thermal stabilization of procaryotic ribosomes by compatiblesolutesB. Seip*, E.A. Galinski, M. KurzUniversität Bonn, Institut für Mikrobiologie und Biotechnologie, Bonn,GermanyRibosomes play an important role in cell metabolism. Besides integrity ofthe cell membrane, ribosomal function is supposed to determine thetemperature limit of life [Gaucher 2008, Lee 2002]. Ribosome stabilityunder physical stress has been investigated for some time but so far theinfluence of the solvent water and its modulation by co-solvents has beenignored.In this context the well-known stabilizing effect of compatible solutes(osmolytes) on proteins is subjected to scrutiny because ribosomes alsocomprise base-paired nucleic acids, for which a destabilizing effect had tobe expected (Lambert 2007).Here we present a first insight into the effects of some protein-stabilizingand -destabilizing low molecular weight osmolytes on E. coli and H.elongata ribosomes under thermal stress. Ribosomal stability in thepresence and absence of co-solutes was investigated using differentialscanning calorimetry according to the methods of Lee [2002] and MackeyBIOspektrum | Tagungsband 2012