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

largely ignored 20 years ago for stability and resilience of soil ecosystems isnowadays better understood and many studies have shown that archaea havethe capacity to contribute to all major nutrient cycles. However there is stilla controversial discussion in literature about activity of archaea in soils andtheir contribution to functional traits like nitrification compared to theirbacterial counterparts.In the presentation data will be presented that confirms the importance ofarchaea for soil quality of agricultural ecosystems and key drivers will bedefined that steer abundance, activity and diversity of functional groupsinvolved in carbon and nitrogen cycle. In additions concepts will bepresented how this new data could be used to understand more about generalquestions related to functional redundancy or ecosystem resilience, theoriesthat were built up for macroecology.EMV010Microbial model systems and ecological theory: How doesincreasing environmental stress affect microbialinteractions and ecosystem services?A. Chatzinotas*, R. Schäwe, M. Saleem, I. Fetzer, H. HarmsHelmholtz Center for Environmental Research (UFZ), Leipzig, GermanyDespite the recently increasing interest in ecological theory, the applicationin microbial ecology is currently still rather limited. One explanation mightbe the sceptical attitude of many ecologist and microbiologist to integrategeneral ecological concepts mainly originating from experiments withhigher organisms into microbial systems.Here we argue that microbial model systems are in particular promising dueto their simplicity and their high degree of control and replication to answerquestions regarding the relationship of biodiversity and ecosystem functions.We established microbial microcosms to investigate the influence ofchanging environmental conditions on microbial performance along adiversity gradient. Current theory suggests that complementarity is a majormechanism explaining a positive relationship between biodiversity andecosystem functioning. We show that exposure to increasing levels ofabiotic stress or additional trophic levels (e.g. predators) results in alteredinter-specific interactions. While under benign environmental conditionscompetition is controlling the communities, mutualism dominates understressed conditions. Moreover, higher microbial diversity seems to be inparticular important to provide sufficient possibilities for positiveinteractions between the members of a community - a relevant insurance formaintaining the functioning of a microbial system under stress.EMV011Disturbance ecology controls natural attenuation incontaminated aquifersG. Pilloni* 1 , A. Bayer 1 , B. Anneser 1 , M. Engel 2 , C. Griebler 1 , T. Lueders 11 Institute of Groundwater Ecology, Helmholtz Center Munich, Neuherberg,Germany2 Institute of Soil Ecology, Max Planck Institute for TerrestrialMicrobiology, Marburg, GermanyDisturbance ecology aims to understand the consequences of perturbation onbiota within ecosystems. For aquifers, which are mainly governed bymicrobes, we are only beginning to grasp their functioning as ecosystems.Especially, aquifers are classically perceived as extremely stableenvironments, where dynamics occur only over long time scales due to theirvery limiting conditions (low temperature, nutrients, oxygen). Also afteranthropogenic pollution, this may require decades for being naturallyattenuated. Yet, the ecological principles governing, and potentially limitingnatural attenuation in aquifers are still poorly understood. Here we unravelhow anaerobic hydrocarbon degraders established in a thin lower fringebeneath a groundwater contaminant plume were unexpectedly disturbed byrelatively minor hydraulic dynamics. Such dynamics have beenhypothesized to either increase (by increasing the mixing) or decrease (byimposing unfavourable conditions on locally established degraders) netcontaminant removal. Fine scale monitoring of hydrogeochemistry as wellas massively paralleled pyrosequencing of bacterial rRNA gene fragmentsobtained over three years of repetitive sampling from different depths of theaquifer was performed. We established bidirectional sequencing of bacterialrRNA gene amplicons (~520 bp) which even allowed for assembly ofamplicon contigs, T-RF prediction and phylogenetic reconstruction. Morethan 135,000 pyrotags helped us to unravel how degrader populations wereaffected by hydraulic dynamics. Prior to the disturbance, a highly selected,low-evenness degrader community of sulfate-reducing toluene degradersdominated by Desulfobulbaceae established at the lower plume fringe wasdetected. After relevant groundwater table dynamics, we observed adramatic collapse of this standing degrader population connected to atransient loss of biodegradation activity. Subsequently, a distinct butfunctionally redundant population of degraders within the Gram-positivePeptococcaceae, over a longer time scale, restored functionality and thusinsured natural attenuation against ecosystem disturbance. These findingshighlight that aquifers are not steady-state habitats, and call for a newunderstanding of the ecological controls of hydraulic disturbance onmicrobes in groundwater ecosystems.EMV012The Baltic Sea microbiome:bacterial transitions along a2000 km salinity gradientD.P.R. Herlemann* 1 , M. Labrenz 1 , K. Jürgens 1 , S. Bertilsson 2 , J.J. Waniek 1 ,A.F. Andersson 31 Biological Oceanography, Leibniz Institute for Baltic Sea ResearchWarnemünde, Rostock, Germany2 Department of Ecology & Genetics, Limnology, Uppsala University,Uppsala, Sweden3 Science for Life Laboratory, KTH Royal Institute of Technology,Stockholm, SwedenAquatic ecosystems are controlled by abiotic environmental factors,including salinity. As early as 1934, Remane described a brackish watertransition zone between salt water and freshwater, inhabited by only a fewbenthic invertebrates living at the edge of their salinity tolerance limits. Yetdespite the abundance and importance of microorganisms in marine aquaticecosystems, it is still unclear how they are distributed along the salinitygradient. We assessed bacterial community succession along the salinitygradient of the Baltic Sea, one of world’s largest brackish waterenvironments, using 454 pyrosequencing of partial (400 bp) 16S rRNAgenes of 213 samples collected along vertical profiles at 60 samplingstations in summer. Along the salinity gradient a change in the bacterialcomposition was manifested at broad phylogenetic levels as well as at finescalephylogenetic levels, with closely related populations occupyingdifferent salinity and depth ranges. A major shift in the bacterialcommunities in the surface water was observed at salinity 8-10 and atsalinity 3-4. Between these abiotic barriers, the bacterial community wascomposed of a diverse combination of freshwater and marine groups, alongwith populations unique to the brackish environment. Since water residencetimes in the Baltic Sea exceeds five years, this brackish bacterial communitycannot be the result of conservative mixing of freshwater and saltwater, butreveals the first detailed description of an autochthonous brackishmicrobiome. In contrast to benthic faunal diversity, a lower bacterialdiversity was not observed at intermediate (brackish) salinity levels, whichsuggests that the rapid adaptation of bacteria has enabled a diversity oflineages to fill what for higher organisms remains a challenging andrelatively unoccupied ecological niche.EMV013Complex interactions between marine phages and theirFlavobacterium hostsL. Riemann* 1 , K. Holmfeldt 2 , M. Middelboe 1 , D. Odic 31 Marine Biological Section, University of Copenhagen, Helsingør, Denmark2 EEB Department, University of Arizona, Tucson, USA3 Department of Cell and Molecular Biology, Uppsala University, Uppsala,SwedenPhages are thought to regulate bacterial community composition throughhost-specific infection and lysis. However, our work with a marineFlavobacterium phage-host system consisting of 40 phages and 21 bacterialstrains suggests that specificity and efficiency of infection and lysis is highlyvariable among phages. Pronounced variations in genome size (8 to >242kb) and host range (infecting 1 to 20 bacterial strains) was found among thephages. Most of the phages had double-stranded DNA genomes; however,DNase I and S1 digestion of 8 phage genomes suggested that these weresingle-stranded DNA phages, consistent with their faint staining by SYBRGold in gels and for microscopy. Further, we were unable to enumerate themby flow cytometry when stained with SYBR Gold or SYBR Green I. Hence,a diverse assemblage of phages was infectious to a suite of Flavobacteriumhosts that were geno- and phenotypically very similar. Further, our dataindicated that susceptibility to infection was strain-specific and thatspektrum | Tagungsband 2011