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

208threat to the health of reefs worldwide, results from the dysfunction andcollapse of the symbiosis. Several studies suggest that coral bleaching is ahost innate immune response to a symbiont compromised by severeoxidative stress. This evidence includes increased nitric oxide levels, andhost cell apoptosis and autophagy in heat-stressed animals, all well-knownimmune mechanisms in other systems to eliminate detrimental microbialinvaders.SIV2-FGAmount, activity and mode of transmission of microbialsymbionts associated with the Caribbean sponge Ectyoplasia feroxV. Gloeckner* 1 , S. Schmitt 1 , N. Lindquist 2 , U. Hentschel 11 University of Wuerzburg, Julius von Sachs Institute for BiologicalSciences, Wuerzburg, Germany2 University of North Carolina at Chapel Hill, Institute of Marine Sciences,Chapel Hill, United StatesMany marine sponges contain large amounts of phylogenetically complexyet highly sponge-specific microbial consortia within the mesohyl matrix.While vertical transmission has been shown in various marine sponges[1,2,3], the impact of horizontal/ environmental transmission has not beeninvestigated so far. This study provides insights into vertical andhorizontal/ environmental transmission of sponge symbionts using adult,embryonic and larval material of the Caribbean sponge Ectyoplasia ferox.Transmission-electron microscopy revealed large amounts ofmorphologically diverse microorganisms in the adult and embryonictissue. Counting of DAPI stained bacteria in adult sponge tissuehomogenates displayed a loss of 50% of the sponge microorganismsduring spawning. By sequencing approximately 250 16S rRNA genelibrary clones and by using a 99% similarity threshold, OTUs wereobtained for adult (44), embryonic (13) and larval (12) sponge material.Denaturing gradient gel electrophoresis (DGGE) showed highly similarbanding patterns between the three developmental stages, indicating thatsponge specific symbionts are transmitted vertically. Activity profiling bycomparing 16S rRNA and 16S rRNA genes via DGGE revealed, thatnearly all symbionts are metabolically active in all three developmentalstages. Initial attempts to create symbiont-free sponge larvae by theaddition of antibiotics were promising. As observed by DGGE, the amountof bacteria inside the larvae could be reduced significantly. Howeversymbiont free sponge larvae were not obtained, likely because of the shortincubation time of four days. In summary, it was shown, that the three E.ferox developmental stages contained highly similar microbial consortia,which confirms previous observations that sponge-specific microbialconsortia are passed on via vertical transmission. These symbionts arefurthermore metabolically active in all developmental stages. In addition,the expulsion of up to 50% of sponge symbiont biomass into theenvironment during spawning and their potential uptake again by othersponges renders horizontal/ environmental transmission at least as anotherpossibility.1. Enticknap, J., Kelly, M., Peraud, O. and Hill, R. (2006). Appl. Environ. Microbiol. 72: 3724-32.2. Schmitt, S., Weisz, J.B., Lindquist, N. and Hentschel, U. (2007). Appl. Environ. Microbiol. 73: 2067-78.3. Sharp, K., Eam, B., Faulkner, D. and Haygood, M. (2007). Appl. Environ. Microbiol. 73: 622-29.SIV3-FGHighly specific nematode symbioses from the North Sea andthe benefits of harbouring ectosymbiontsJ. Zimmermann* 1 , J.M. Petersen 1 , J. Ott 2,3 , N. Musat 1 , N. Dubilier 11 Max Planck Institute for Marine Microbiology, Molecular Ecology,Symbiosis Group, Bremen, Germany2 University of Vienna, Department of Molecular Ecology, Vienna, Austria3 University of Vienna, Department of Marine Biology, Vienna, AustriaEctosymbiotic bacteria are widespread on marine organisms but thespecificity of these associations and the beneficial role of the symbiontsare still poorly understood. Stilbonematid nematodes from sulfidic coastalsediments carry a characteristic coat of sulfur-oxidizing ectosymbionts ontheir cuticle. It is widely believed that these ectosymbionts providenutrition to their hosts but no clear evidence has been provided so far. Toinvestigate specificity and the role of ectosymbiotic bacteria we looked atstilbonematid nematodes of the genus Leptonemella from intertidal sandysediments of the North Sea island of Sylt. To date, three co-occuringLeptonemella species have been described from Sylt based on theirmorphology. Our first aim was to investigate the specificity of theLeptonemella symbioses by using molecular methods. Phylogeneticanalysis based on the 18S rRNA marker gene of the nematodes revealed anunexpectedly high diversity of at least five Leptonemella species that areclosely related to Leptonemella species from the Mediterranean Sea. Clonelibraries of the 16S rRNA gene and the ribosomal intergenic spacer region(ITS) of the ectosymbionts showed that these are closely related to thegammaproteobacterial sulfur-oxidizing ectosymbionts of other nematodehost species as well as the endosymbionts of gutless marine andoligochaetes (the so-called MONTS clade for Marine Oligochaete andNematode Symbionts). Remarkably, each of the five host species has itsown distinct 16S-ITS rRNA symbiont phylotype, indicating that theseectosymbioses are highly specific, despite the fact that the hosts co-occurand acquire their symbionts from the environment. Our second aim was totest the hypothesis that the ectosymbionts provide their hosts withnutrition. We incubated the worms and their symbionts with radiolabelledbicarbonate and measured inorganic carbon fixation by the symbionts andtransfer of fixed carbon to the host. We developed a method to separate theectosymbionts from the worms so that the radioactive label could bemeasured in each separately. With this method we showed that thesymbionts incorporate radiolabelled carbon, which is then transferred to thehost. We are currently using nanoscale secondary ion mass spectrometry(NanoSIMS) on Leptonemella tissue sections to examine the transfer of carbonin more detail. Our results show that there is a high degree of specificity in theectosymbiotic associations of these very closely related co-occurring hostspecies and that the hosts benefit nutritionally from their symbionts.SIV4-FGDigesting the diversity - evolutionary patterns in the gutmicrobiota of termites and cockroachesT. Köhler*, C. Dietrich, A. BruneMax Planck Institute for Terrestrial Microbiology, Department ofBiogeochemistry, Marburg, GermanyFrom a phylogenetic viewpoint, termites are a family of socialcockroaches. In addition, close relatives of bacterial lineages consideredtypical for termite intestinal tracts have also been occasionally found incockroach guts. This gives rise to the hypothesis that elements of the gutmicrobiota found in different termite lineages are derived from theircommon evolutionary ancestors. However, the microbial diversity in theguts of every termite family has not been fully explored, and even less isknown about the microbiota of cockroach guts. We comprehensivelyanalyzed the bacterial communities in the microbe-packed hindguts of 34dictyopteran species by amplification of the V3-V4 region of bacterial 16SrRNA genes with a modified primer set and subsequent 454 pyrotagsequencing. The communities were analyzed both on the basis of sequencesimilarity and according to hierarchical classification. Thorough statisticaland community analyses revealed that the cockroach gut microbiota ismore diverse and less specialized than that of termites. The bacterialcommunity compositions differed significantly already at the phylumlevel. Nevertheless, we found a core microbiota of groups ofLachnospiraceae, Synergistaceae, and other taxa in all insectsinvestigated, which strongly supports the hypothesis that elements of thetermite gut microbiota were present already in the common ancestor. Aremarkable increase in relative abundance of certain bacterial lineagescorrelates with the feeding guilds, which indicates that the gut microbiotaprovides a reservoir of bacterial diversity that is exploited when newfunctions are required, e.g., for the degradation of particular dietarycomponents. Taken together, the emerging patterns document a longhistory of (co)evolution between the gut microbiota and their dictyopteranhost species, resulting in a clear and distinct clustering of the bacterialcommunities that reflects both the phylogeny and the feeding guild of theirhosts.SIV5-FGMetabolic activity of the obligate intracellular amoeba symbiontProtochlamydia amoebophila in a host-free environmentA. Siegl* 1 , B.S. Sixt 1 , C. Müller 2 , M. Watzka 3 , A. Richter 3 , P. Schmitt-Kopplin 2 , M. Horn 11 University of Vienna, Department of Microbial Ecology, Vienna, Austria2 Helmholtz-Zentrum Muenchen - German Research Center for EnvironmentalHealth, Institute of Ecological Chemistry, Department of MolecularBioGeoChemistry and Analytics, Neuherberg3 University of Vienna, Department of Chemical Ecology and EcosystemResearch, ViennaPrior to 1997, chlamydiae were exclusively perceived as pathogens ofhumans and animals, and our knowledge about their biology was restrictedto members of the family Chlamydiaceae, including the human pathogensChlamydia trachomatis and Chlamydia pneumoniae. Today we know thatthe true diversity within the phylum Chlamydiae is larger than everthought before. Many of the more recently discovered chlamydiae exist inphylogenetically diverse hosts in the environment. One of the eightcurrently known chlamydial families, the Parachlamydiaceae, is wellknown to comprise natural symbionts of free-living amoebae. A commonfeature of all chlamydiae is their obligate intracellular lifestyle whichcomes along with a unique biphasic developmental cycle. The so calledelementary body (EB) constitutes the infective form and was perceived asa spore-like stage which is metabolically inert. However, recent studieschallenged this dogma and provided first evidence for an extracellularactivity of EBs. The aim of this study was the characterization of themetabolic capabilities of EBs of the amoeba symbiont Protochlamydiaamoebophila. For this purpose, EBs were purified from their host cells andincubated with isotope-labeled substrates in a host-free environment.Isotope-ratio mass spectrometry (IRMS) and fourier transform ionBIOspektrum | Tagungsband 2012