VAAM-Jahrestagung 2011 Karlsruhe, 3.–6. April 2011

structural changes, most significantly the movement of Glu150 from a diironbridging in the oxidized, to a not ligating position in the semi reducedsubstrate bound state. In contrast to other members of the class I diironenzyme family the position of benzoyl-CoA inside a 20 Å long channel isaccurately known indicating that the C2 and C3 atoms of its phenyl ring arecloser to one of the irons (Fe1), and that the attacking oxygen of activatedO 2 is essentially ligated to Fe1. We postulate a reaction cycle with a radicalattack of this oxygen on C2 leading to a delocalization over the CoAthioester as the essential step. The substrate bound structure doubtlesslyindicates the stereoselective 2S,3R-epoxide formation by BoxB.[1] Zaar, A. et al (2001): A novel pathway of aerobic benzoate catabolism in the bacteria Azoarcusevansii and Bacillus stearothermophilus. J Biol Chem, 276(27): p. 24997-5004.[2] Rather, L.J et al (2010): Coenzyme A-dependent aerobic metabolism of benzoate via epoxideformation. J Biol Chem. 285(27): p. 20615-24.[3] Rather, L.J. et al: Structure and mechanism of the diiron benzoyl coenzyme A epoxidase BoxB, tobe published.EMP030Bacterial succesion and enzyme activity in two glacierforefield chronosequences on Larsemann Hills, EastAntarcticaF. Bajerski*, L. Padur, D. WagnerPeriglacial Research, Alfred Wegener Institute for Polar and MarineResearch, Geomicrobiology, Potsdam, GermanyBeside the Antarctic Peninsula, the Prydz Bay area in East Antarctica is oneof the main regions affected by global warming[1][2]. Increasingtemperatures lead to the retreat of glaciated areas, whereby new terrain isbecoming exposed to soil formation and accessible for microbialcolonisation. On the one hand it is important to find out how these habitatsdevelop due to climate change, on the other hand Antarctic glacier forefieldsprovide a unique opportunity as a natural laboratory to study primarysuccession in connection to microbial communities in extremeenvironments. A polyphasic approach, containing geochemical andmicrobiological examinations, will be used to describe the habitatcharacteristics and the complex system of microbial communities in twoglacier forefield chronosequences on Larsemann Hills, East Antarctica.Preliminary results in molecular fingerprinting (DGGE) indicate a higherdiversity in the vicinity of the glaciers, which is being confirmed by T-RFLPanalysis. Enrichment cultures on two different media were used to determinethe number of cultivable heterotrophs and to isolate and characterise selectedmicroorganism. The number of cultivable heterotrophs increases withincreasing distance to the glacier. Isolates obtained from the GlacierTransect could be classified as Actinobacteridae, Sphingobacteria,Flavobacteria and Alpha- and Betaproteobacteria. Additional classes in theBlack Valley Transect are Cytophagia, Gammaproteobacteria andDeinococci. Actinobacteridae dominate in both transects. Present resultssuggest a lower microbial density but higher diversity in the vicinity of theglacier. A colonisation gradient along the chronosequences could beassumed but will have to be proven in further analyses. Furthermore enzymeactivity tests for protease, urease, saccharase, glucosidase and phosphataseshall reveal how microbial processes are related to nutrient and energyfluxes in the initial developing habitat.[1] Temperature increases in the Antarctic due to climate change, 2090 (NCAR-CCM3, SRES A2experiment). (2008). In UNEP/GRID-Arendal Maps and Graphics Library. Retrieved 11:17,December 13, 2010 from http://maps.grida.no/go/graphic/temperature-increases-in-the-antarctic-dueto-climate-change-2090-ncar-ccm3-sres-a2-experiment.[2] J. Turner et al (2005): Antarctic climate change during the last 50 years. International Journal OfClimatology 25, 279-294.EMP031Dynamics of methane cycling microbial communities indegrading permafrost-affected ecosystems on HerschelIsland, Canadian Western ArcticB. Barbier*, D. WagnerAlfred Wegener Institute for Polar and Marine Research, PeriglacialResearch, Potsdam, Germany Potsdam, GermanyIn the current context of climate change, the main goal of the researchpresented is to elucidate the fate of organic carbon stored in permafrost bylooking at microbial-driven carbon degradation in the active layer ofpermafrost affected soils from Herschel Island in the Canadian WesternArctic. The abundance, dynamics and function of microbial communitiesinvolved in consuming this organic carbon is analysed, especially thoseinvolved in methane production and consumption. Microorganisms involvedin methane cycling are of particular relevance in frozen environments, asrising permafrost temperatures eventually lead to an increased degradationof previously conserved organic matter. This in turn leads to an increasedmethanogenic activity, creating a potentially dangerous positive feedbackloopfor climate change. The point of focus here is the biodiversity andfunction of methanogenic and methanotrophic microorganisms thriving insuch difficult conditions and their reaction to warming temperatures and arapidly changing environment.Undergoing research activities include terminal-restriction fragment lengthpolymorphism (T-RFLP) analysis of methanogenic and methanotrophiccommunities in an active layer profile from Herschel Island, showingpreferential colonisation of the middle and lower anaerobic layers bymethanogenic archaea (5cm to 35cm depth) and of the higher, aerobic layersby methanotrophic bacteria (0cm to 20cm depth). Incubation experimentsunder controlled variables at 10°C with no added substrate revealed a highmethane production rate from middle (3.2 nmol g -1 h -1 at 15cm depth) andlower (3 nmol g -1 h -1 close to the permafrost table) active layer samples, anda lower but nonetheless consequent methanogenic activity in the uppersediment layers. Soil characteristics including soil moisture, C/N ratio, totalorganic carbon content and grain size were also investigated in order to helpelucidate the observed distribution of microorganisms. Active layer samplesgenerally have a high water content (41-88%) and very high organic carboncontent (20-42%). The results obtained are being scrutinized to elucidate theadaptability of methane cycling microbial communities and the fate oforganic carbon in the active layer.EMP032Application of two-dimensional compound-specificisotope analysis for aerobic and anaerobic oxidation ofethylbenzeneC. Dorer*, C. Vogt, H.-H. RichnowDepartment of Isotope Biogeochemistry, Helmholtz Center forEnvironmental Research (UFZ), Leipzig, GermanySome microorganisms have the ability to degrade environmentallydangerous hydrocarbons such as BTEX compounds (benzene, toluene,ethylbenzene, xylenes). Compound-specific isotope analysis (CSIA) is amethod to detect and quantify in situ biodegradation processes. It is based onthe observation that enzymes prefer molecules containing lighter stableisotopes (e.g. 12 C, 1 H) over the ones containing heavier stable isotopes (e.g.13 C,2 H). Measurement of isotope ratios of two elements may provideadditionally insight into the reaction mechanisms and thus distinguishbetween different pathways or predominant redox-conditions. This isexpressed by the slope Λ of the linear regression for hydrogen (Dd 2 H)versus carbon (Dd 13 C) discrimination. The factor Λ can be seen as afingerprint of the initial biochemical bond cleavage reaction within a distinctdegradation pathway.We applied two-dimensional CSIA to investigate aerobic and anaerobicoxidation of ethylbenzene by microorganisms using different degradationpathways. Ethylbenzene dehydrogenase is the initial enzyme in thedenitrifying Aromatoleum aromaticum strain EbN1. It is able to oxidize theside-chain of non-activated ethylbenzene without molecular oxygen as cosubstrate.The naphthalene dioxygenase of Pseudomonas putida NCIB9816-4 has a relaxed substrate specificity and catalyzes the benzylicmonooxygenation and dioxygen-dependent alcohol oxidation ofethylbenzene. Although both enzymes lead to the same intermediate (S)-1-phenethyl alcohol, our results show different Λ values for both pathways.This indicates that both reaction mechanisms can be principallydistinguished by two-dimensional isotope fractionation analysis.Furthermore we can demonstrate that the cytochrome P-450-likenaphthalene dioxygenase shows especially low Λ factors for initial BTEXattackingreactions compared to other monohydroxylations.EMP033Bacterial Identification for Environmental MonitoringUsing MALDI-TOFS. Polson, M. Patel*Accugenix, Marketing, Newark, USAMost technologies and databases designed for rapid identification ofmicroorganisms are designed with clinical isolates in mind. When adaptedfor use in the microorganism monitoring programs of pharmaceutical,spektrum | Tagungsband 2011