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

or pharmaceutical industry, could be increased to 2800 U/mL, more thantenfold as compared to previous processes [3]. In current work, 13 C-basedmetabolic flux analysis was used to quantify the underlying carbon coremetabolism of A. niger under different production conditions including thecomparison of different mutants as well as morphological forms. Thispromises valuable insights towards the further development of A. niger as acell factory for recombinant proteins.[1] Driouch, H. et al (2010): Morphology engineering of Aspergillus niger for improved enzymeproduction. Biotechnol Bioeng; 105:1058-68.[2] Driouch H. et al (2010): Optimized bioprocess for production of fructofuranosidase byrecombinant Aspergillus niger. Appl Microbiol Biotechnol 87:2011-24.[3] Driouch H. et al (2010): Filamentous fungi in good shape: Microparticles for tailor-made fungalmorphology and enhanced enzyme production. Bioengineered Bugs (In press).SIV001A Screen to identify fungal and plant signals duringarbuscule formation in AM symbiosisC. Vogt*, H. Kuhn, N. RequenaBotanical Institute, Plant-Microbial-Interactions, Karlsruhe Institute ofTechnology (KIT), Karlsruhe, GermanyThe great success of arbuscular mycorrhiza (AM) symbiosis relies on themutualistic exchange of nutrients between the vast majority of all land plantsand the Glomeromycotan fungi. Most important for this interchange is thearbuscule as main organ of nutrition exchange. This fungal structure is buildinside the root cortex cells via invagination of the plasma membranefollowed by an intense dichotomous branching of the fungal hyphae. Theformation of the arbuscule requires a complex exchange of signals betweenthe two partners. The plant’s cellular program must be adjusted to allow theentry of the hyphae and to initiate the rearrangement necessary for theaccommodation of the fungus in the cell.The Phosphate Transporter 4 of Medicago truncatula (MtPT4) is located inthe periarbuscular membrane of the cortex cells, delivering the phosphateprovided by the fungus to the plant [1]. The presence of this mycorrhizaspecific expressed protein has been shown to be essential for properarbuscule development indicating a role of MtPT4 during this process [2].In order to identify fungal and plant proteins involved in the control of thearbuscule formation we developed a screen to search for factors that are ableto drive the expression of MtPT4 as a reporter gene for the onset ofarbuscule formation.[1] Harrison, M.J. et al (2002): A Phosphate Transporter from Medicago truncatula Involved in theAcquisition of Phosphate Released by Arbuscular Mycorrhizal Fungi. The Plant Cell 14: 2413-2429.[2] Javot, H et al (2007): A Medicago truncatula phosphate transporter indispensable for thearbuscular mycorrhizal symbiosis. Proceedings of the National Academy of Sciences 104: 1720-1725.SIV002An effector protein from the symbiotic fungus G.intraradices suppresses plant early defense responsesS. Kloppholz*, H. Kuhn, N. RequenaBotanical Institute, Plant-Microbial Interactions, Karlsruhe Institute ofTechnology (KIT), Karlsruhe, GermanyFor many microbial pathogens the delivery of effector proteins represents acrucial mechanism to manipulate their host and to enable colonization. Weshow that the symbiotic mycorrhizal fungus G. intraradices secretes thesmall, tandem repeat protein SP7 that targets the pathogenesis-relatedtranscription factor ERF19 at the nucleus of its host plants. ERF19 is highlyinduced in roots infected with the fungal pathogen Colletotrichum trifolii butonly transiently upregulated during early mycorrhizal colonization. Thelevel of C. trifolii-mediated induction of ERF19 can be reduced by theconstitutive expression of SP7 in planta. Additionally these roots exhibit ahigher mycorrhization status than control root lines after 5 and 12 days postinoculation with G. intraradices. Furthermore, expression of SP7 in the riceblast fungus M. oryzae attenuates root decay symptoms. Arbuscularmycorrhizal spore extracts highly induce ERF19 as well as pathogenesisrelatedproteins 10a/b expression in control roots, while this is softened inSP7 expressing lines. Our results suggest that SP7 is an effector thatcontributes to establish/maintain the biotrophic status of arbuscularmycorrhizal fungi in roots by counteracting the early plant immuneresponse.SIV003Drugs from bugs that kill bugs: Biosynthesis and functionof natural products from entompathogenic bacteriaH.B. BodeInstitute for Molecular Bio Science, Goethe-University, Frankfurt am Main,GermanyPhotorhabdus and Xenorhabdus live in symbiosis with Heterorhabditis andSteinernema nematodes, respectively. The bacteria-nematode complex ishighly entomopathogenic and is used in organic farming to kill differentinsect pests. Moreover, the difference between symbiosis (towards thenematode) and pathogenesis (towards the insects) can be studied using thesebacteria and we have started to look in detail into the role of bacterialsecondary metabolites, which might play a role in both processes. In the lastfew years we could identify (i) novel secondary metabolites, (ii) theircorresponding biosynthesis gene clusters, and (iii) could also proposefunctions to some of these compounds within the complex life cycle ofbacteria, nematodes, and insects. Examples are the isopropylstilbenes,unusual urea derivatives, a family of new linear peptides, the xenocoumacinantibiotics, simple amides and indole derivatives as well as anthraquinones.Additionally, the formation of small molecules specific for different stagesof the complex bacterial life style as well as the activation of the respectivebiosynthesis gene clusters under lab conditions will be presented and theirfunction will be discussed.SIV004Host selection shapes microbial community structure incockroach gutsC. Thompson*, C. Schauer, A. BruneDepartment of Biogeochemistry, Max Planck Institute for TerrestrialMicrobiology, Marburg, GermanyTermites harbor a diverse microbial community within their intestinal tractsthat allows them to digest wood and other lignocellulosic diets. While thecomposition of such assemblages is easily established, the influence of thehost on community structure and the role of gut microorganisms in hostdevelopment remain uncertain. Greater insights into such reciprocalinteractions could be obtained from gnotobiotic models, but due to theirelaborate social system termites cannot be raised under germ-freeconditions. As an alternative, we developed a gnotobiotic model of thecockroach Shelfordella lateralis. These cockroaches are non-social, can beraised under germ-free conditions, and are closely related to termites. Weinoculated gnotobiotic cockroaches with a full complement of termite gutmicrobiota and determined the resulting bacterial community structure by454 pyrosequencing of 16S rRNA genes. While certain members of thetermite gut microbiota successfully colonized the cockroach gut, otherlineages were completely lost. This demonstrates the importance of hostselection in shaping the structure of the intestinal microbial community. Inaddition, we found that in the absence of a gut microbiota, host developmentwas severely impaired but maturation was achieved after the animals wereconventionalized with cockroach gut microbiota. We expect that our modelwill also provide further insights into the digestive symbiosis.SIV005Immune response of the ant Camponotus floridanusagainst pathogens and its obligate mutualisticendosymbiontR. Gross* 1 , H. Feldhaar 2 , C. Ratzka 11 Chair of Microbiology, Julius-Maximilians-University, Würzburg,Germany2 Chair of Behavioural Biology, University of Osnabrück, Osnabrück,GermanyInsects rely on innate defense mechanisms to combat infections. Whereasthe immune system of Drosophila melanogaster is well characterized [1],much less is known in other insects, and in particular in social insects [2].Thus, we focused on the characterization of the innate immune system of thecarpenter ant Camponotus floridanus. This ant species harbours the obligateendosymbiont Blochmannia floridanus in bacteriocytes [3] and is thereforealso an interesting model organism to study the interactions between hosts,endosymbionts and pathogens.As a first step towards characterizing the ant´s immune response, we usedsuppression subtractive hybridization (SSH) to identify genes that arespektrum | Tagungsband 2011