No description available.

Als "surface-layer" (S-Layer, SL) bezeichnet man die regelmäßig strukturierten Hüllproteinlagen auf der Oberfläche von etwa 80 % aller bisher bekannten Bakterienspezies. Sie entstehen durch Selbstassemblierung von identischen Proteinuntereinheiten, die wiederum zumeist durch nichtkovalente Wechselwirkungen mit der darunterliegenden Zellwandkomponente verknüpft sind. Trotz ihrer Diversität auf der Ebene der Primärstruktur weisen S-Layer verschiedener Bakterienarten einheitliche physikochemische Merkmale auf. Dazu zählt u.a. die Wiedereinnahme einer hochgradig strukturierten, porösen Proteinschicht nach reversibler Denaturierung. Infolge der Reassemblierung entstehen sowohl in Lösung als auch an Phasengrenzen Proteinassemblate, deren Porenanordnungen die gleiche regelmäßige Symmetrie aufweisen, wie die nativen Hüllproteine auf der Bakterienzelle. Das in seiner Domänenstruktur aufgeklärte Hüllprotein SbsC des mesophilen Bakterienstammes Geobacillus (G.) stearothermophilus ATCC 12980 zeichnet sich durch eine ausgezeichnete Synthetisierbarkeit in E. coli aus. C-terminale Fusionen, die im Falle des verstärkt grün fluoreszierenden Proteins (EGFP) bis zu 240 Aminosäuren umfassen, führten nicht zu einem Verlust der Selbstassemblierung. Darüber hinaus zeigen in vitro gebildete SbsC-Assemblate eine außergewöhnliche Stabilität gegenüber hohen Ethanolkonzentrationen. Die durch gerichtete Mutagenese erzeugten SbsC-Fusionsproteine SbsC(aa 31-1099)-HspA und SbsC(aa 31-1099)-12His besitzen in assemblierter Form im Vergleich mit dem unmodifizierten Protein eine bis zu zweimal höhere Bindungsaffinität gegenüber Platinionen. In denaturierter Form waren beide Fusionsproteine in der Lage, Nickelionen zu komplexieren. In der vorliegenden Arbeit wurde erstmals ein SL-Protein in einem eukaryontischen Mikroorganismus produziert. Das in der Hefe S. cerevisiae gebildete Fusionsprotein SbsC(aa 31-1099)-EGFP assembliert dabei im Cytosol der Wirtszellen zu röhrenförmigen Assemblaten mit regelmäßiger Symmetrie. Das bisher unbekannte SL-Protein des Stammes G. stearothermophilus DSM 13240 wurde erfolgreich heterolog in E. coli exprimiert. Die Vorläuferform besitzt im Vergleich zum maturen Protein ein 31 aa umfassendes Sekretionssignal am extremen N-Terminus. Sowohl das authentische Protein als auch das heterolog in E. coli exprimierte Vorläuferprotein zeigen eine dem SbsC-Protein vergleichbare Reassemblierungscharakteristik. Im Gegensatz dazu führte die Verkürzung der N-terminalen 30 Aminosäuren des als S13240 bezeichneten Hüllproteins im heterologen System zu einem irreversiblen Verlust der Fähigkeit zur Selbstassemblierung.

Benzene is chemically stable as it has no substituents which can be biochemically attacked and a well-known toxic contaminant whose anaerobic degradation pathway is still not fully resolved. As only a very few anaerobic benzene-mineralizing pure cultures have been described yet, research was usually done with enrichment cultures dominated by specific organisms capable of benzene degradation under different electron acceptor conditions. Remarkable progress has been made in recent years with regard to the initial mechanism of benzene transformation especially on the putative genes that are involved in anaerobic carboxylation of benzene and the benzoyl-CoA central pathway. Many phylotypes described to be primary benzene degraders in anaerobic enrichment cultures at various electron acceptor conditions belong to the Peptococcaceae. Here, the thesis focused on characterizing the structure and function of anaerobic benzene-mineralizing microbial communities enriched from two hydrocarbon-contaminated sites: hydrocarbon-contaminated sediment from Ogoni in Niger Delta of Nigeria and a benzene-contaminated aquifer in Zeitz (Germany). The Niger Delta is one of the world’s most damaged ecosystem mainly due to hydrocarbon exploration accidents. The natural attenuation potential of Niger Delta subsurface sediment for anaerobic hydrocarbon degradation was investigated using benzene as a model compound under iron-reducing, sulfate-reducing, and methanogenic conditions. Benzene was slowly mineralized under iron-reducing conditions using Fe(III) chelated with nitrilotriacetic acid, or poorly crystalline Fe(III) oxyhydroxides as electron acceptors, analyzed by measurement of 13CO2 produced from added 13C-labelled benzene. The highest mineralization rates were observed in microcosms amended with Fe(III) oxyhydroxides while microcosms amended with Fe(III) nitrilotriacetic acid produced methane. Abundant phylotypes were affiliated to Betaproteobacteriales, Ignavibacteriales, Desulfuromonadales, and Methanosarcinales of the genera Methanosarcina and Methanothrix, illustrating that the enriched benzene mineralizing communities were diverse and may contain more than a single benzene degrader. The study underpins the importance of microbial ecosystem services in contaminant degradation as a sustainable environmental means of mitigating harmful chemicals. Benzene degradation pathways in a benzene-mineralizing, nitrate-reducing enrichment culture from Zeitz was investigated. Benzene mineralization was dependent on the presence of nitrate and correlated to enrichment of a Peptococcaceae phylotype only distantly related to known anaerobic benzene degraders of this family. Its relative abundance decreased after benzene mineralization had terminated, while other abundant taxa - Ignavibacteriaceae, Rhodanobacteraceae and Brocadiaceae - slightly increased. Generally, the microbial community remained diverse despite amendment of benzene as single organic carbon source, suggesting complex trophic interactions between different functional groups. A subunit of the putative anaerobic benzene carboxylase (AbcA) previously detected in Peptococcaceae was identified by metaproteomic analysis suggesting that benzene was activated by carboxylation. Detection of proteins involved in anaerobic ammonium oxidation (Anammox) indicates that benzene mineralization was accompanied by Anammox, facilitated by nitrite accumulation and the presence of ammonium in the growth medium. The results suggest that benzene was activated by carboxylation and further assimilated by a novel Peptococcaceae phylotype and confirm the hypothesis that Peptococcaceae are important anaerobic benzene degraders. Only a few benzene mineralizing anaerobes have been isolated to date. In an attempt using classical isolation techniques to isolate benzene-mineralizing pure cultures from a benzene-mineralizing nitrate-reducing microbial community, two consortia were gained under nitrate-reducing conditions spiked separately with acetate and benzene as sole sources of carbon and energy with media containing ammonium or without ammonium. Both consortia – Bz4 (with ammonium) and Bz7 (without ammonium) - mineralized 13C-labelled acetate under anoxic conditions at 3.3 and 2.7 µM day-1, respectively, revealed by analysis of evolved 13CO2. However, only Bz4 mineralized 13C-labelled benzene (0.298 µM benzene mineralized day-1) generated up to 960.2 ± 0.3 ‰ ẟ13C-CO2 during 184 days while producing only slight amounts of nitrite (4.60 ± 0.004 µM). By 16S rRNA gene amplicon sequencing was determined that the isolated cultures were not pure cultures but still contained several different phylotypes. The gained Bz4 consortium that mineralized benzene under anoxic conditions can be further purified and explored for their metabolic potentials.:Acknowledgments ………………………………………………………................. ii Table of Contents …………………………………………………………………… iii Dissertation Summary ……………………………………………………………… vi Dissertation Zusammenfassung …………………………………………………… viii List of Tables ………………………………………………………………………… x List of Figures ……………………………………………………………………….. xi List of Appendices ………………………………………………………………….. xiii Abbreviations .………………………………………………………….................... xv Chapter 1: Introduction and Research Objectives ……………………………… 1 1.1 Introduction ……………………………………………………………… 2 1.2 Aims and Objectives ………………………………………………….... 4 Chapter 2: Anaerobic Benzene Degradation by Microbial Communities and Pure Cultures …… 6 2.1 Anaerobic benzene degradation – a brief introduction ...…………… 7 2.2 Anaerobic benzene degradation under different electron acceptor conditions … 9 2.2.1 Benzene degradation under methanogenic conditions ……… 9 2.2.2 Benzene degradation under sulfate-reducing conditions …… 14 2.2.3 Benzene degradation under nitrate-reducing conditions …… 20 2.2.4 Benzene degradation under iron-reducing conditions ……… 25 2.3 Anaerobic benzene degradation by pure cultures ………………… 26 2.4 Anaerobic benzene activation mechanisms and associated genes……………… 28 2.4.1 Hydroxylation of benzene …………………………………….… 30 2.4.2 Methylation of benzene ………………………………..………… 34 2.4.3 Carboxylation of benzene ……………………………....………. 34 2.5 Benzoyl-CoA central metabolic pathways ………………………… 37 2.6 Syntrophic interactions in benzene-degrading communities ……… 42 2.7 Prospects for the future ……..……………………………………………… 43 Chapter 3: Anaerobic Benzene Mineralization by Natural Microbial Communities from Niger Delta …………………………………………………………………........... 44 3.1 Introduction …………………………………………………………..... 45 3.2 Materials and Methods ……………………………………………….. 46 3.2.1 Chemicals ………………………………………………………... 46 3.2.2 Site description and sampling procedure ……………………… 47 3.2.3 Setup of enrichment cultures …………………………………… 47 3.2.4 Chemical and microscopic analysis …………………………… 48 3.2.5 Microbial community analysis …………………………………… 49 3.3 Results and Discussion …………………………………………………. 50 3.3.1 Mineralization of benzene at different electron-acceptor conditions …………... 50 3.3.2 Microbial community structure at different electron-acceptor conditions ……... 53 3.4 Conclusion ………………………………………….…………………… 61 Chapter 4: Structure and Functional Capacity of a Benzene-mineralizing, and Nitrate-reducing Microbial Community ……………………………………………......... 62 4.1 Introduction …………………………………………………………..... 63 4.2 Materials and methods ……………………………………………..... 64 4.2.1 Chemicals ………………………………………………………... 64 4.2.2 Microcosm setup and sampling ………………………………… 64 4.2.3 Chemical and physiochemical analyses ……………………… 66 4.2.4 Amplicon and metagenome sequencing ……………………… 67 4.2.5 Protein mass spectrometry ……………………………………. 67 4.2.6 Metaproteome analysis ………………………………………… 68 4.2.7 Cloning and sequencing of putative nitric oxide dismutase (nod) genes ………. 68 4.2.8 Data availability …………………………………………………… 69 4.3 Results …………………………………………………………………………. 70 4.3.1 Benzene mineralization under nitrate-reducing conditions …… 70 4.3.2 Changes in microbial diversity during benzene mineralization . 71 4.3.3 Metaproteome composition ……………………………………… 74 4.3.4 Presence of putative nitric oxide dismutase genes (nod) ……. 76 4.4 Discussion ……………………………………………………………... 76 4.4.1 Putative pathways for nitrate reduction coupled with benzene mineralization … 76 4.4.2 Elucidation of the benzene activation step ……………………… 78 4.4.3 Benzoyl-CoA central pathway ……………………………………. 79 4.4.4 Peptococcacea as putative primary benzene degraders ……… 80 4.4.5 Metabolic function of Anammox bacteria in the community …… 81 Chapter 5: Consortia Dominated by Gammaproteobacteria Isolated from a Denitrifying Benzene-degrading Enrichment Culture and their Capacity to Mineralize Benzene...................... 83 5.1 Introduction ……………………………………………………………… 84 5.2 Materials and methods ………………………………………………… 85 5.2.1 Chemicals ………………………………………………………… 85 5.2.2 Isolation procedure …………………………………………………… 85 5.2.3 Mineralization and nitrite analyses ……………………..……… 86 5.2.4 Genomic DNA extraction and 16S rRNA gene sequencing … 87 5.3 Results …………………………………………………………………. 87 5.4 Discussions …………………………………………………………… 91 Chapter 6: General Conclusions and Outlook …..……………………………… 95 6.1 Conclusions and novelty of the research …………………………… 96 6.2 Ignavibacteriales as benzene degrading consortia under iron-reducing conditions 96 6.3 Insights into benzene activation via carboxylation by Peptococcaceae … 97 6.4 Unraveling growth of Anammox bacteria during benzene mineralization … 98 6.5 Study significance ……………………………………………………… 99 6.6 General outlook ………………………………………………………… 100 References ………………………………………………………………………… 101 Appendices ………………………………………………………………………… 120 Contributions of other Authors …………………………………………………… 160

Some of anaerobic, mesophilic sulfate-reducing bacteria that produce H₂S and cause microbial metal corrosion can degrade crude oil in anaerobic conditions. In this study, a mesophilic sulfate-reducing bacterial strain D107G3 isolated from Bach Ho gas-oil field in Vung Tau, Vietnam that is able to utilize crude oil in the anaerobic condition is reported. The strain D107G3 was classified as a Gram-negative bacterium by using Gram staining method. Basing on scanning microscopy observation, the cell of a strain D107G3 had a curved rod shape. The 16S rRNA gene sequence analysis showed that the strain D107G3 was identified as Desulfovibrio vulgaris with 99.7% identity. The suitable conditions for its growth that was determined via estimating its H₂S production was the modified Postgate B medium containing 1% (v/v) crude oil, 1% NaCl (w/v), pH 7 and 300C incubation. In these conditions, the strain D107G3 can consume 11.4 % of crude oil total and oxidize heavy crude oil (≥ C45) for one month at anoxic condition. These obtained results not only contribute to the science but also continue to warn about the dangers of mesophilic sulfate reducing bacteria to the process of crude oil exploitation, use, and storage in Vung Tau, Vietnam. / Trong bài báo này, chủng vi khuẩn khử sunphat (KSF) ưa ấm D107G3 phân lập từ giếng khoan dầu khí mỏ Bạch Hổ, Vũng Tàu, Việt Nam có khả năng sử dụng dầu thô trong điều kiện kị khí được công bố. Chủng D107G3 được xác định là vi khuẩn Gram âm nhờ phương pháp nhuộm Gram. Quan sát trên kính hiển vi điện tử quét cho thấy tế bào chủng D107G3 có hình que cong. Kết quả phân tích trình tự gen 16S rRNA đã xác định được chủng D107G3 thuộc loài Desulfovibrio vulgaris với độ tương đồng 99.7%. Thông qua đánh giá lượng H₂S tạo thành đã khám phá được điều kiện thích hợp cho sinh trưởng của chủng D107G3: môi trường Postgate B cải tiến chứa 1% (v/v) dầu thô, 1 % NaCl (gL⁻¹), pH 7 và nuôi cấy ở 30°C. Trong điều kiện đó, chủng D107G3 đã sử dụng được 11.4 % hàm lượng dầu tổng số, thành phần dầu bị phân huỷ là các n-parafin có mạch C≥45 sau 1 tháng nuôi cấy kỵ khí. Các kết quả này đóng góp về mặt khoa học và tiếp tục cảnh báo mối nguy hại của KSF ưa ấm đến việc khai thác, sử dụng và bảo quản dầu mỏ ở Vũng Tàu, Việt Nam.

Agarwood mainly formed by Aquilaria species is an economically and pharmaceutically important natural product used for the production of incense, perfumes and traditional medicines in Asia. Endophytic bacteria are potentially important in producing pharmaceutical compounds found in the plants. The aim of this research is to isolate, classify and identify major endophytic bacteria groups associated with agarwood of Aquilaria crassna species in Khanh Hoa province, Vietnam. Agarwood samples were collected and surface-sterilized, and total endophytic bacteria were isolated on Tryptic Soy Agar by the spread plate method. Major bacterial groups were classified according to the Bergey’s system. The 16S rRNA gene fragments were amplified using PCR method, and bacterial isolates were identified using this gene sequence similarity based method. The results showed that from 0.121 g of agarwood, total 26 bacterial isolates were purified and divided into 7 separated groups, in which the group II of Gram-positive spore-forming bacteria was the most dominant. Especially, two dominant strains, T14 of group II, and T15 of group VII, were identified as Bacillus pumilus and Alcaligenes faecalis, respectively.!To our knowledge, it is the first time that biodiversity of bacterial endophytes associated with agarwood from Aquilaria crassna in Vietnam has been reported, which requires of further study to understand the relationship of endophytic bacteria to agarwood-producing Aquilaria crassna species as well as explore their potential applications towards the development of valuable bioactive compounds. / Trầm hương, chủ yếu được tạo ra từ các loài cây Dó (Aquilaria), là một sản phẩm tự nhiên có giá trị kinh tế và y học đã được sử dụng để sản xuất hương, nước hoa và các dược phẩm truyền thống ở châu Á. Vi khuẩn nội cộng sinh thực vật được cho là một nguồn quan trọng cho các dược phẩm có nguồn gốc thực vật. Mục tiêu của nghiên cứu này là nhằm phân lập, phân loại và định danh các nhóm vi khuẩn chính trên Trầm hương Khánh Hòa, Việt Nam. Các mẫu Trầm hương được thu nhận và vô trùng bề mặt dùng để phân lập vi khuẩn tổng số trên môi trường TSA bằng phương pháp trải đĩa. Các nhóm vi khuẩn chính được phân loại dựa theo hệ thống chuẩn Bergey. Đoạn gen mã hóa 16S rRNA được khuếch đại bằng phương pháp PCR, và các chủng vi khuẩn được định danh bằng phép so sánh độ tương đồng trình tự của đoạn gen này. Kết quả cho thấy từ 0,121 g mẫu trầm hương, chúng tôi đã phân lập được 26 chủng vi khuẩn và phân chúng vào 7 nhóm chính, trong đó nhóm II bao gồm các vi khuẩn Gram dương sinh bào tử là nhóm chiếm ưu thế nhất. Đặc biệt, có 2 chủng ưu thế là chủng T14 thuộc nhóm II và chủng T15 thuộc nhóm VII đã được định danh tương ứng là Bacillus pumilus và Alcaligenes faecalis.!Đây là nghiên cứu đầu tiên về đa dạng sinh học của các nhóm vi khuẩn chính trên Trầm hương Khánh Hòa. Vì vậy, cần có những nghiên cứu tiếp theo nhằm tìm hiểu mối quan hệ giữa các vi khuẩn nội cộng sinh với cây Dó bầu (Aquilaria crassna) tạo trầm cũng như khai thác những ứng dụng tiềm năng của các vi khuẩn này theo hướng phát triển các hoạt chất sinh học có giá trị.

This article studies the impact of some environmental conditions and the nutrition of culturing medium on the growth of bacteria and theirs capacity of toluene removal. The 5 bacterial strains isolated from leaf samples of three different common houseplants in Vietnam are Gram-negative, rod-shaped bacteria. The cells are single or arranged in chains. The cell size is relatively small and ranged from 0.7 to 2.5μm. These bacteria prefer the incubating temperature from 28°C to 32°C and a neutral pH 6.5 to 7.5. They are able to assimilate different nitrogen and carbon sources. In the liquid SH1 medium containing 200ppm toluene five selected strains have shown the ability to degrade toluene at a rate of 12.8 to 75.2% in comparison with the control at 30°C at a speed of 200rpm for over 120 hours. These 5 studied strains are potentially useful in bioremediation strategies to remove airborne toluene. / 5 chủng vi khuẩn có khả năng phân giải toluene được phân lập từ lá một số cây cảnh phổ biến ở Việt Nam là vi khuẩn G (-), dạng trực khuẩn và kích thước tế bào từ 0,7 – 2,5μm. Một số điều kiện môi trường nuôi cấy thích hợp cho 5 chủng vi khuẩn nghiên cứ gồm nhiệt độ 28°C-32°C, pH 6,5- 7,5, có khả năng đồng hoá nhiều nguồn nitơ và ba nguồn carbon khác nhau. Trong điều kiện môi trường dịch SH1 chứa 200ppm toluene, 5 chủng vi khuẩn này cho thấy khả năng phân giải toluene từ 12,8 – 75,2%. Đây là các chủng vi khuẩn có tiềm năng ứng dụng để loại bỏ toluene từ không khí ô nhiễm.

The rising number of antibiotic resistant bacteria (ARB) may introduce to the post antibiotic era because they cause a loss of the therapeutic potential of antibiotics. For many years the important role of the natural environment as reservoir and dissemination pathway for ARB and responsible genes has been largely overlooked. However, especially aquatic ecosystems provide optimal conditions for the antibiotic resistance (AR) evolution: first, aquatic ecosystems are frequently affected by anthropogenic activities that cause multiple pollutions for example with heavy metals, that potentially cause co-selection of antibiotic- and heavy metal resistance. Second, aquatic ecosystems feature a dissemination pathway between human populations and natural environments via the urban water cycle. Water cycles between human associated environments (e.g. house holds and clinics) via waste water through waste water treatment plants into natural ecosystems (e.g. water bodies) and back as drinking water after purification. Third, ecosystem internal biotic interactions such as competition between bacteria and predation by the natural consumers seem to impact AR evolution sustainably. The present doctoral thesis focuses on the impact of abiotic and biotic factors on the proliferation of AR and responsible genes in natural aquatic environments, with special emphasis on (i) heavy metal driven co-selection of antibiotic and heavy metal resistance and (ii) on the impact of competition and predation on the evolution of AR. In order to quantify the risk of heavy metal driven co-selection for AR spread, I provide a first risk assessment based on literature values of environmental heavy metal loadings and related AR. Additionally, I developed a limit value named minimum co-selective concentration (MCC), which is the lowest concentration of a heavy metal that can potentially cause coselection in nature. It turned out that Cu, Zn, Ni, Hg, and Cd are suspected to be the main co-selecting heavy metals in the aquatic environment. I further investigated heavy metal driven co-selection of AR in a river ecosystem, the Western Bug River (Ukraine). I found indications for co-selection of resistance to five antibiotics (ciprofloxacin, gentamicin, amikacin, tobramycin, and cefepime) and two metals (Ni and Cd) caused by Ni- and Cd-levels. Both metals exceed their MCC for water samples and Cd additionally in sediments. As a second focal point the present work emphasis on ecological interactions effecting AR evolution. Currently three possible effects of ecological interactions on AR spread are discussed. First, environmental antibiotic levels are rather low, however they might favour ARB due to a competitive advantage. The reason is that even sublethal antibiotic levels reduce the growth of sensitive bacteria while resistant cells remain unaffected by the antibiotic action. Second, predation by protozoa is believed to impact conjugation between prey bacteria (and thus the transfer of DNA and potential resistance genes) by keeping bacteria in a growing stage that favours conjugation. Third, in order to escape predation by protozoa, bacteria evolved grazing defence mechanisms such as the formation of inedible biofilms, which can feedback on the evolution of AR. With an ordinary differential equation model, I tested the effect of low antibiotic levels and losses (e.g. due to predation) on the proliferation of ARB in a modelled planktonic system. In case that the model contains the mechanism that conjugation frequencies are highest during exponential growth, I found that (i) (grazing) losses enhance conjugation frequencies between bacteria and that (ii) medium levels of antibiotics and (grazing) losses favour resistant cells in the competition to sensitive bacteria. Biofilms are thought to be \'hot spots\' for conjugation but some plasmids have lower conjugation frequencies in biofilms compared to planktonic systems. As a first step, in order to discover predation effects on plasmid spread in plankton - biofilm systems I investigated grazing resistance of bacteria in grazing experiments. Both plankton and biofilm phenotypes were consumed, when exposed to their specialized grazer (either plankton-feeder or biofilmfeeder), whereas the other phenotype remained grazing-resistant and thus became the dominant prey type. Both predators together effectively control planktonic and biofilm prey. With regards to the spread of AR-genes via conjugation, I speculate that the feeding preference of the present predator can affect the invasion success of resistance plasmids in planktonic - biofilm systems. For dynamic systems, I assume that dynamics of predator and prey traits (plankton vs. biofilm-feeder and biofilm vs. planktonic prey) will lead to dynamics of conjugation frequencies in planktonic or biofilm bacteria. I assume that conjugation events are more frequent in the dominant prey type (plankton or biofilm). However, other factors such as pili-type of the plasmid (short and rigid pili, prefers conjugation in biofilms or long and flexible pili, prefers conjugation in plankton) might additionally influence plasmid invasion success in plankton - biofilm morphotypes.

Durch die Freisetzung allelopathisch aktiver Substanzen können Makrophyten das Wachstum von Phytoplankton beeinflussen und damit den Klarwasserzustand von Flachseen stabilisieren. Umweltfaktoren beeinflussen allelopathische Effekte und wurden untersucht, um die Bedeutung allelopathischer Effekte im Ökosystem einzuschätzen. Der Gehalt allelopathisch aktiver polyphenolischer Substanzen zeigte Schwankungen bis zu einer Größenordung im Apikalmeristem von Myriophyllum verticillatum L innerhalb von vier Jahren 2004-2007, die nur teilweise durch den Nährstoffgehalt in der Pflanze erklärt wurden. Der Gehalt an Polyphenolen in der Trockenmasse der Pflanze korrelierte mit der Wachstumshemmung von Anabaena variabilis im Biotest und zeigte Maxima im Mai bis Juli wenn Konkurrenz mit dem Phytoplankton um Licht beim Wachstum zur Wasseroberfläche besteht. Mittels HPLC und MS gelang die Identifizierung von Hexahydroxydiphenoyl di- und -tri-galloylglucose Isomeren in den hauptaktiven Fraktionen des Pflanzenextraktes. Abiotische und biotische Einflüsse der Umwelt auf die Allelochemikalie z.B. photolytische und mikrobielle Umwandlungsprozesse führten bei der Modellsubstanz Tanninsäure (TA), die in Struktur und Funktion den gefundenen Allelochemikalien ähnelt, zur Bildung von refraktären hochmolekularen Verbindungen mit anhaltender allelopathischer Wirkung, die mittels LC-OCD den Huminstoffe zugeordnet wurden. Temperatur als weiterer Umweltfaktor beeinflusste artspezifisch die Reaktion der untersuchten Algen auf TA. Dabei waren die Art und das Ausmaß der Reaktion von der Anwesenheit von Bakterien abhängig. Bakterien der Gattung Pseudomonas wurden isoliert, die in der Lage waren, TA abzubauen und deren allelopathische Effekte zu mindern. Es konnten gezeigt werden, dassl Umwelteinflüsse auf die Allelochemikalie, mutualistische Phytoplankton-Bakterien Interaktionen und die Zusammensetzung der Bakteriengemeinschaft allelopathische Effekte qualitativ als auch quantitativ beeinflussten. / Dissolved organic compounds released by macrophytes can have allelopathic effects on phytoplankton and thereby contribute to stabilize the clear water state of shallow lakes. Identifying factors influencing allelopathy enables evaluating allelopathic effects in the ecosystem.One factor is the temporal dynamic of allelopathically active substances and was investigated as total phenolic compounds(TPC). TPC ranged by an order of magnitude in apicals of Myriophyllum verticillatum L. during four years (2004-2007). Nutrient content partly explained TPC dynamic. The highest amounts of TPC in plant tissue corresponded to maximal growth inhibition of Anabaena variabilis in biotest from May to July when macrophytes compete with algae for light to grow to the water surface. Isomers of Hexahydroxydiphenoyl -di- and -trigalloylglucose identified by HPLC and LC-MS were found in the most allelopathically active fractions in the biotest. By the use of analytical and molecularbiological methods photolytic transformation and degradation by bacteria, changes in mutualistic interaction of bacteria and phytoplankton and shifts in bacterial community composition were identified as factors influencing the allelochemical and the phytoplankton response to TA quantitatively and qualitatively. Photolytic and microbial transformation formed long lasting allelopathically active degradation products of an allelopathic test substance, tannic acid (TA). Temperature was shown to influence the phytoplankton response to TA species specifically varying with presence or absence of bacteria. Bacteria community composition mediated phytoplankton response and specific bacteria as Pseudomonas sp.were able to degrade allelochemicals as TA and thereby lowered the allelopathic effect. Thus, allelopathic effects can be influenced by abiotic and biotic factors acting on the allelochemical, the target organisms and on mutualistic interaction between target organisms altering the outcome of allelopathic effects.

No description available.

Aufgrund der ökologischen und ökonomischen Problematik der chemischen Phosphatfällung ist eine Optimierung der Effizienz und Stabilität der biologischen Verfahren zur Phosphat-elimination erforderlich. Hierfür ist jedoch ein fundiertes Wissen über die daran beteiligten Organismen eine entscheidende Vorraussetzung. Das Ziel der vorliegenden Arbeit war es, die mikrobielle Populationstruktur von zwei Belebtschlamm-anlagen im Labormaßstab mit Hilfe von drei unterschiedlichen 16S rDNA basierenden molekular-biologischen Methoden zu charakterisieren. Ein besonderer Schwer-punkt ist hierbei die Analyse der Bakterien, die mit der erhöhten biologischen Phosphat-elimination in Verbindung gebracht werden. Dies sind Vertreter der Rhodocyclus-Gruppe, der Gattung Tetrasphaera und der Gattung Acinetobacter. Als Untersuchungsobjekte wurden zwei Hauptstromverfahren zur erhöhten biologischen Phosphatelimination gewählt, die sich im Schlamm-alter, der Schlammbelastung und der sich daraus resultierenden Nitrifikationsleistung unterscheiden. Aufgrund der gewählten Verfahrensweisen wurde der Einfluss der Nitrifikation auf die Zusammensetzung der Belebtschlammbiozönose ebenfalls untersucht. Um praxisnahe Verhältnisse zu erreichen, wurden die Anlagen mit kommunalem Abwasser beschickt. Für einen Vergleich sollten Proben aus kommunalen Kläranlagen mit deutlich anderen Verfahrensweisen in die Untersuchungen mit einbezogen werden.