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

[1]. Interestingly, the locus located in 34.6-34.8 centisome region of thechromosome encodes six different prepeptides, but only one candidatelanthionine synthase for their chemical transformation. To determinewhether all prepeptides are processed by a single promiscuous enzyme, aseries of co-expression experiments was conducted in E. coli and monitoredby MALDI-TOF MS. The results indicated that the annotated lanthioninesynthase readily dehydrates all six prepeptides notwithstanding theirstructural differences in the C-terminal region. Moreover, it was revealedthat three lanthionine rings are formed in the peptides upon action of theenzyme.[1] Begley, M. Et al (2009): Appl. Environ. Microbiol., 75, 5451- 5460.[2] Li, B. Li et al (2010): Proc. Natl. Acad. Sci. USA, 107, 10430-10435.EMP082Occurrence of Roseobacter subclusters in the GermanBight of the North SeaS. Billerbeck*, H.-A. Giebel, M. SimonInstitute for Chemistry and Biology of the Marine Environment (ICBM),Carl von Ossietzky University, Oldenburg, GermanyThe Roseobacter clade of Alphaproteobacteria is an important componentof the marine bacterioplankton. Studies all over the world havedemonstrated that members of this clade can constitute large proportions oftotal Bacteria which can vary greatly, seasonally and as a function ofenvironmental factors. Most of the Roseobacter clusters identified in pelagicenvironments consist predominantly of uncultured phylotypes and onlyscarce information exists on the simultaneous occurrence of distinctsubclusters.In order to elucidate the occurrence of the major pelagic subclusters of theRoseobacter clade, we investigated these subclusters during a phytoplanktonspring bloom in May in the German Bight of the North Sea. Due to the factthat members of the Roseobacter clade are often found in association withalgae we sampled stations in- and outside the phytoplankton bloom andanalysed the particle-associated (PA, >5 μm) and the free-living (FL, 0,2-5μm) fraction for the presence of the following subclusters: RCA, NAC11-6,NAC11-7, CHAB-I-5 and SH6-1. DNA extracted from the PA and FLbacterial fractions was analysed by PCR with cluster-specific primers.Further, we applied DGGE of 16S rRNA gene fragments amplified withprimers specific for the Roseobacter clade. In addition inorganic nutrients(phosphate, nitrate and nitrite), dissolved amino acids, plankton-relatedparameters (chlorophyll, POC, suspended particulate matter) and bacterialcell counts were assessed.All five clusters of interest were detected in the investigated area butpredominantly in the FL bacterial fraction. However, only the RCA andSH6-1 clusters were detected consistently in the entire area. The otherclusters were not detected at all stations and exhibited less uniform patterns,e.g. the NAC11-6 cluster was not detected at the stations with the highestconcentrations of chlorophyll a (13-15 μg Chl l -1 ). The Roseobacter-specificDGGE showed rather diverse banding patterns and a higher number ofbands in the PA fraction than in the FL bacterial fraction, especially atstations with high chlorophyll concentrations. The Roseobacter communityof the PA and FL bacterial fractions showed pronounced differences asrevealed by a cluster analysis.EMP083Role of light in the survival of the aerobic anoxygenicphototroph Dinoroseobacter shibae during starvationM. Soora*, H. CypionkaInstitute for Chemistry and Biology of the Marine Environment (ICBM),Carl von Ossietzky University, Oldenburg, GermanyDinoroseobacter shibae was isolated from a culture of marinedinoflagellates. The strain belongs to the Roseobacter clade and is anaerobic anoxygenic phototroph (AAP; Biebl et al, 2005). AAPs are capableof using light as a source of energy under oxic conditions without thegeneration of oxygen. They possess light-harvesting systems, reactionCenter, bacteriochlorophyll a (Bchl a) and carotenoids with spheroidenoneas a major component. Light was shown to induce ATP formation andproton translocation by the cells [Holert et al, 2010]. However, the cells donot grow by light energy alone. Instead there is only a certain level of lightdependentincrease in the amount of biomass, protein and pigmentconcentrations [Biebl et al, 2006].Our question is under which conditions does light have the maximumcompetitive advantages for the bacteria. Accordingly, we tested thepostulates (i) that the role of light energy for the cellular metabolism isproportional to the degree of starvation and (ii) that the metabolism isspecifically adapted to the day-and-night rhythm. Batch cultures of D.shibae were maintained for several months under starvation in a) the dark, b)under continuous illumination and c) under dark-light cycles. To record thephysiological fitness respiration, chemiosmotic proton translocation and theadenylate energy charge were determined.[1] Biebl, H. et al (2005): Dinoroseobacter shibae gen. nov., sp. nov., a new aerobic phototrophicbacterium isolated from dinoflagellates. Int J Syst Evol Microbiol 55: 1089-1096.[2] Holert, J. (2010): Influence of light and anoxia on chemiosmotic energy conservation inDinoroseobacter shibae. Environmental Microbiology Reports, no. doi:10.1111/j.1758-2229.2010.00199.x[3] Biebl, H., and I. Wagner-Döbler (2006): Growth and bacteriochlorophyll a formation intaxonomically diverse aerobic anoxygenic phototrophic bacteria in chemostat culture: influence oflight regimen and starvation. Process Biochem 41: 2153-2159.EMP084Genome mining in the plant pathogen RalstoniasolanacearumM. Kreutzer*Junior Research Group Secondary Metabolism of Predatory Bacteria,Leibniz Institute for Natural Product Research and Infection Biology, HansKnöll Institute, Jena, GermanyGenomic analyses have unveiled the tremendous potential ofmicroorganisms for natural product biosynthesis and have initiated aparadigm shift in isolation programs from bioassay-guided fractionation togenome mining. By means of computational sequence comparison tools andbiosynthetic precedence, the structures of many previously unobservedmetabolites can be predicted from genomic data, which in turn allows thedevelopment of suitable fermentation and genetic methods to activate orenhance their production.This work is focused on the secondary metabolism of Ralstoniasolanacearum, a Gram-negative soil bacterium that causes bacterial wilt insolanaceous plants like tomato, potato and tobacco [1]. Analysis of thegenome sequence of this phytopathogen revealed the presence of abiosynthetic gene cluster related to the yersiniabactin locus from the plaguebacterium Yersinia pestis. Variation of culture conditions eventually led tothe activation of the biosynthetic genes in Ralstonia solanacearum andenabled an isolation of the encoded metabolite. The subsequent structureelucidation unveiled a molecular architecture which, albeit related toyersiniabactin, was not expected from computational analysis.[1] Gabriel et al (2006): MPMI, 9, 1, 69-79EMP085Analysis of nitrogen transforming microbial communitiesin shallow and deep karstic aquifersS. Opitz* 1 , K. Küsel 1 , T. Ward 2 , K.U. Totsche 2 , M. Herrmann 11Institute of Ecology, Aquatic Geomicrobiology, Friedrich-Schiller-University, Jena, Germany2 Institute of Earth Sciences, Department of Hydrogeology, Friedrich-Schiller-University, Jena, GermanyMicrobial nitrogen transformation processes in aquifers play an importantrole for the suitability of groundwater as a drinking water resource.However, only little is known about the microbial communities mediatingthose processes in aquifer systems. In this study, we are analyzing samplestaken from karstic limestone aquifers at different depths ranging from 12 to88 meters. Sampling sites are arranged along a gradient from forest toagriculturally used land in the national park Hainich (Thuringia/Germany).Here, high levels of oxygen availability in the groundwater with an oxygensaturation of up to 50 % point to an important role of aerobic nitrogentransforming processes. Therefore, our goal is to investigate seasonal andspatial patterns in the community composition, abundance, andtranscriptional activity of microorganisms mediating the first and ratelimitingstep of nitrification, the oxidation of ammonia, using the amoAgeneas a molecular marker. Preliminary results obtained with a combinedDGGE/cloning approach suggest differences in the community compositionof ammonia oxidizing bacteria and ammonia oxidizing archaea betweendifferent depths as well as between different sampling times. Moreover, atsome sites, elevated concentrations of nitrate in the groundwater coincidewith increased bacterial amoA gene copy numbers as determined byspektrum | Tagungsband 2011