570 Biowissenschaften; Biologie
Refine
Year of publication
- 2017 (235) (remove)
Document Type
- Article (127)
- Doctoral Thesis (46)
- Postprint (44)
- Other (8)
- Review (7)
- Habilitation Thesis (2)
- Part of a Book (1)
Is part of the Bibliography
- yes (235)
Keywords
- ancient DNA (4)
- phylogeny (4)
- Cyanobacteria (3)
- Myodes glareolus (3)
- Southeast Asia (3)
- biogeography (3)
- body height (3)
- community effect (3)
- oxidative stress (3)
- phylogeography (3)
Institute
- Institut für Biochemie und Biologie (196)
- Mathematisch-Naturwissenschaftliche Fakultät (18)
- Institut für Ernährungswissenschaft (16)
- Institut für Chemie (2)
- Department Sport- und Gesundheitswissenschaften (1)
- Extern (1)
- Institut für Geowissenschaften (1)
- Institut für Mathematik (1)
- Institut für Physik und Astronomie (1)
- Strukturbereich Kognitionswissenschaften (1)
Exploring the Arabidopsis metabolic landscape by genetic mapping integrated with network analysis
(2017)
Background: The relative dose response (RDR) test, which quantifies the increase in serum retinol after vitamin A administration, is a qualitative measure of liver vitamin A stores. Particularly in preterm infants, the feasibility of the RDR test involving blood is critically dependent on small sample volumes. Objectives: This study aimed to assess whether the RDR calculated with retinol-binding protein 4 (RBP4) might be a substitute for the classical retinol-based RDR test for assessing vitamin A status in very preterm infants. Methods: This study included preterm infants with a birth weight below 1,500 g (n = 63, median birth weight 985 g, median gestational age 27.4 weeks) who were treated with 5,000 IU retinyl palmitate intramuscularly 3 times a week for 4 weeks. On day 3 (first vitamin A injection) and day 28 of life (last vitamin A injection), the RDR was calculated and compared using serum retinol and RBP4 concentrations. Results: The concentrations of retinol (p < 0.001) and RBP4 (p < 0.01) increased significantly from day 3 to day 28. On day 3, the median (IQR) retinol-RDR was 27% (8.4-42.5) and the median RBP4-RDR was 8.4% (-3.4 to 27.9), compared to 7.5% (-10.6 to 20.8) and -0.61% (-19.7 to 15.3) on day 28. The results for retinol-RDR and RBP4-RDR revealed no significant correlation. The agreement between retinol-RDR and RBP4-RDR was poor (day 3: Cohen's κ = 0.12; day 28: Cohen's κ = 0.18). Conclusion: The RDR test based on circulating RBP4 is unlikely to reflect the hepatic vitamin A status in preterm infants.
Import and decomposition of dissolved organic carbon in pre-dams of drinking water reservoirs
(2017)
Dissolved organic carbon (DOC) depicts a key component in the aquatic carbon cycle as well as for drinking water production from surface waters. DOC concentrations increased in water bodies of the northern hemisphere in the last decades, posing ecological consequences and water quality problems. Within the pelagic zone of lakes and reservoirs, the DOC pool is greatly affected by biological activity as DOC is simultaneously produced and decomposed. This thesis aimed for a conceptual understanding of organic carbon cycling and DOC quality changes under differing hydrological and trophic conditions. Further, the occurrence of aquatic priming was investigated, which has been proposed as a potential process facilitating the microbial decomposition of stable allochthonous DOC within the pelagic zone.
To study organic carbon cycling under different hydrological conditions, quantitative and qualitative investigations were carried out in three pre-dams of drinking water reservoirs exhibiting a gradient in DOC concentrations and trophic states. All pre-dams were mainly autotrophic in their epilimnia. Discharge and temperature were identified as the key factors regulating net production and respiration in the upper water layers of the pre-dams. Considerable high autochthonous production was observed during the summer season under higher trophic status and base flow conditions. Up to 30% of the total gained organic carbon was produced within the epilimnia. Consequently, this affected the DOC quality within the pre-dams over the year and enhanced characteristics of algae-derived DOC were observed during base flow in summer. Allochthonous derived DOC dominated at high discharges and oligotrophic conditions when production and respiration were low. These results underline that also small impoundments with typically low water residence times are hotspots of carbon cycling, significantly altering water quality in dependence of discharge conditions, temperature and trophic status. Further, it highlights that these factors need to be considered in future water management as increasing temperatures and altered precipitation patterns are predicted in the context of climate change.
Under base flow conditions, heterotrophic bacteria preferentially utilized older DOC components with a conventional radiocarbon age of 195-395 years before present (i.e. before 1950). In contrast, younger carbon components (modern, i.e. produced after 1950) were mineralized following a storm flow event. This highlights that age and recalcitrance of DOC are independent from each other. To assess the ages of the microbially consumed DOC, a simplified method was developed to recover the respired CO2 from heterotrophic bacterioplankton for carbon isotope analyses (13C, 14C). The advantages of the method comprise the operation of replicate incubations at in-situ temperatures using standard laboratory equipment and thus enabling an application in a broad range of conditions.
Aquatic priming was investigated in laboratory experiments during the microbial decomposition of two terrestrial DOC substrates (peat water and soil leachate). Thereby, natural phytoplankton served as a source of labile organic matter and the total DOC pool increased throughout the experiments due to exudation and cell lysis of the growing phytoplankton. A priming effect for both terrestrial DOC substrates was revealed via carbon isotope analysis and mixing models. Thereby, priming was more pronounced for the peat water than for the soil leachate. This indicates that the DOC source and the amount of the added labile organic matter might influence the magnitude of a priming effect. Additional analysis via high-resolution mass spectrometry revealed that oxidized, unsaturated compounds were more strongly decomposed under priming (i.e. in phytoplankton presence). Given the observed increase in DOC concentrations during the experiments, it can be concluded that aquatic priming is not easily detectable via net concentration changes alone and could be considered as a qualitative effect.
The knowledge gained from this thesis contributes to the understanding of aquatic carbon cycling and demonstrated how DOC dynamics in freshwaters vary with hydrological, seasonal and trophic conditions. It further demonstrated that aquatic priming contributes to the microbial transformation of organic carbon and the observed decay of allochthonous DOC during transport in inland waters.
The role of serum amyloid A and sphingosine-1-phosphate on high-density lipoprotein functionality
(2017)
The high-density lipoprotein (HDL) is one of the most important endogenous cardiovascular protective markers. HDL is an attractive target in the search for new pharmaceutical therapies and in the prevention of cardiovascular events. Some of HDL’s anti-atherogenic properties are related to the signaling molecule sphingosine-1-phosphate (S1P), which plays an important role in vascular homeostasis. However, for different patient populations it seems more complicated. Significant changes in HDL’s protective potency are reduced under pathologic conditions and HDL might even serve as a proatherogenic particle. Under uremic conditions especially there is a change in the compounds associated with HDL. S1P is reduced and acute phase proteins such as serum amyloid A (SAA) are found to be elevated in HDL. The conversion of HDL in inflammation changes the functional properties of HDL. High amounts of SAA are associated with the occurrence of cardiovascular diseases such as atherosclerosis. SAA has potent pro-atherogenic properties, which may have impact on HDL’s biological functions, including cholesterol efflux capacity, antioxidative and anti-inflammatory activities. This review focuses on two molecules that affect the functionality of HDL. The balance between functional and dysfunctional HDL is disturbed after the loss of the protective sphingolipid molecule S1P and the accumulation of the acute-phase protein SAA. This review also summarizes the biological activities of lipid-free and lipid-bound SAA and its impact on HDL function.
White adipose tissue (WAT) is actively involved in the regulation of whole-body energy homeostasis via storage/release of lipids and adipokine secretion. Current research links WAT dysfunction to the development of metabolic syndrome (MetS) and type 2 diabetes (T2D). The expansion of WAT during oversupply of nutrients prevents ectopic fat accumulation and requires proper preadipocyte-to-adipocyte differentiation. An assumed link between excess levels of reactive oxygen species (ROS), WAT dysfunction and T2D has been discussed controversially. While oxidative stress conditions have conclusively been detected in WAT of T2D patients and related animal models, clinical trials with antioxidants failed to prevent T2D or to improve glucose homeostasis. Furthermore, animal studies yielded inconsistent results regarding the role of oxidative stress in the development of diabetes. Here, we discuss the contribution of ROS to the (patho)physiology of adipocyte function and differentiation, with particular emphasis on sources and nutritional modulators of adipocyte ROS and their functions in signaling mechanisms controlling adipogenesis and functions of mature fat cells. We propose a concept of ROS balance that is required for normal functioning of WAT. We explain how both excessive and diminished levels of ROS, e.g. resulting from over supplementation with antioxidants, contribute to WAT dysfunction and subsequently insulin resistance.
Background
The hypopharyngeal gland of worker bees contributes to the production of the royal jelly fed to queens and larvae. The gland consists of thousands of two-cell units that are composed of a secretory cell and a duct cell and that are arranged in sets of about 12 around a long collecting duct.
Results
By fluorescent staining, we have examined the morphogenesis of the hypopharyngeal gland during pupal life, from a saccule lined by a pseudostratified epithelium to the elaborate organ of adult worker bees. The hypopharyngeal gland develops as follows. (1) Cell proliferation occurs during the first day of pupal life in the hypopharyngeal gland primordium. (2) Subsequently, the epithelium becomes organized into rosette-like units of three cells. Two of these will become the secretory cell and the duct cell of the adult secretory units; the third cell contributes only temporarily to the development of the secretory units and is eliminated by apoptosis in the second half of pupal life. (3) The three-cell units of flask-shaped cells undergo complex changes in cell morphology. Thus, by mid-pupal stage, the gland is structurally similar to the adult hypopharyngeal gland. (4) Concomitantly, the prospective secretory cell attains its characteristic subcellular organization by the invagination of a small patch of apical membrane domain, its extension to a tube of about 100 μm in length (termed a canaliculus), and the expansion of the tube to a diameter of about 3 μm. (6) Finally, the canaliculus-associated F-actin system becomes reorganized into rings of bundled actin filaments that are positioned at regular distances along the membrane tube.
Conclusions
The morphogenesis of the secretory units in the hypopharyngeal gland of the worker bee seems to be based on a developmental program that is conserved, with slight modification, among insects for the production of dermal glands. Elaboration of the secretory cell as a unicellular seamless epithelial tube occurs by invagination of the apical membrane, its extension likely by targeted exocytosis and its expansion, and finally the reorganisation of the membrane-associated F-actin system. Our work is fundamental for future studies of environmental effects on hypopharyngeal gland morphology and development.
Background
The hypopharyngeal gland of worker bees contributes to the production of the royal jelly fed to queens and larvae. The gland consists of thousands of two-cell units that are composed of a secretory cell and a duct cell and that are arranged in sets of about 12 around a long collecting duct.
Results
By fluorescent staining, we have examined the morphogenesis of the hypopharyngeal gland during pupal life, from a saccule lined by a pseudostratified epithelium to the elaborate organ of adult worker bees. The hypopharyngeal gland develops as follows. (1) Cell proliferation occurs during the first day of pupal life in the hypopharyngeal gland primordium. (2) Subsequently, the epithelium becomes organized into rosette-like units of three cells. Two of these will become the secretory cell and the duct cell of the adult secretory units; the third cell contributes only temporarily to the development of the secretory units and is eliminated by apoptosis in the second half of pupal life. (3) The three-cell units of flask-shaped cells undergo complex changes in cell morphology. Thus, by mid-pupal stage, the gland is structurally similar to the adult hypopharyngeal gland. (4) Concomitantly, the prospective secretory cell attains its characteristic subcellular organization by the invagination of a small patch of apical membrane domain, its extension to a tube of about 100 μm in length (termed a canaliculus), and the expansion of the tube to a diameter of about 3 μm. (6) Finally, the canaliculus-associated F-actin system becomes reorganized into rings of bundled actin filaments that are positioned at regular distances along the membrane tube.
Conclusions
The morphogenesis of the secretory units in the hypopharyngeal gland of the worker bee seems to be based on a developmental program that is conserved, with slight modification, among insects for the production of dermal glands. Elaboration of the secretory cell as a unicellular seamless epithelial tube occurs by invagination of the apical membrane, its extension likely by targeted exocytosis and its expansion, and finally the reorganisation of the membrane-associated F-actin system. Our work is fundamental for future studies of environmental effects on hypopharyngeal gland morphology and development.
We studied the short- (12 h) and long-term (144 h) response of Daphnia pulex lipases to quality shifts in diets consisting of different mixtures of the green alga Scenedesmus with the cyanobacterium Synechococcus, two species with contrasting lipid compositions. The lipase/esterase activity in both the gut and the body tissues had fast responses to the diet shift and increased with higher dietary contributions of Synechococcus. When screening the Daphnia genome for TAG lipases, we discovered a large gene-family expansion of these enzymes. We used a subset of eight genes for mRNA expression analyses and distinguished between influences of time and diet on the observed gene expression patterns. We identified five diet-responsive lipases of which three showed a sophisticated short- and long-term pattern of expression in response to small changes in food-quality. Furthermore, the gene expression of one of the lipases was strongly correlated to lipase/esterase activity in the gut suggesting its potentially major role in digestion. These findings demonstrate that the lipid-related enzymatic machinery of D. pulex is finely tuned to diet and might constitute an important mechanism of physiological adaptation in nutritionally complex environments.
We studied the short- (12 h) and long-term (144 h) response of Daphnia pulex lipases to quality shifts in diets consisting of different mixtures of the green alga Scenedesmus with the cyanobacterium Synechococcus, two species with contrasting lipid compositions. The lipase/esterase activity in both the gut and the body tissues had fast responses to the diet shift and increased with higher dietary contributions of Synechococcus. When screening the Daphnia genome for TAG lipases, we discovered a large gene-family expansion of these enzymes. We used a subset of eight genes for mRNA expression analyses and distinguished between influences of time and diet on the observed gene expression patterns. We identified five diet-responsive lipases of which three showed a sophisticated short- and long-term pattern of expression in response to small changes in food-quality. Furthermore, the gene expression of one of the lipases was strongly correlated to lipase/esterase activity in the gut suggesting its potentially major role in digestion. These findings demonstrate that the lipid-related enzymatic machinery of D. pulex is finely tuned to diet and might constitute an important mechanism of physiological adaptation in nutritionally complex environments.
Cellular membranes constantly experience remodeling, as exemplified by morphological changes during endo- and exocytosis. Regulation of membrane morphology is essential for these processes. In this work, we attempt to establish a regulation path based on the use of photoswitches exhibiting conformational changes in model membranes, namely, giant unilamellar vesicles (GUVs). The mechanism of the changes in the GUVs’ morphology caused by isomerization of the photosensitive molecules has been previously explored but still remains elusive. We examine the morphological reshaping of GUVs in the presence of the photoswitch o-tetrafluoroazobenzene (F-azo) and show that the mechanism behind the resulting morphological changes involves both an increase in the membrane area and generation of a positive spontaneous curvature. First, we characterize the partitioning of F-azo in a single-component membrane using both experimental and computational approaches. The partition coefficient calculated from molecular dynamic simulations agrees with experimental data obtained with size-exclusion chromatography. Then, we implement the approach of vesicle electrodeformation in order to assess the increase in the membrane area, which is observed as a result of the conformational change of F-azo. Finally, the local and the effective membrane spontaneous curvatures were estimated from the observed shapes of vesicles exhibiting outward budding. We then extend the application of the F-azo to multicomponent lipid membranes, which exhibit a coexistence of domains in different liquid phases due to a miscibility gap between the lipids. We perform initial experiments to investigate whether F-azo can be employed to modulate the lateral lipid packing and organization. We observe either complete mixing of the domains or the appearing of disordered domains within the domains of more ordered phase. The type of behavior observed in response to the photoisomerization of F-azo was dependent on the used lipid composition. We believe that the findings introduced here will have an impact in understanding and controlling both lipid phase modulation and regulation of the membrane morphology in membrane systems.
Biodiversity and intact ecological interactions form the basis for functional and resilient ecosystems that maintain optimal conditions for life on earth. During the second half of the 20th century, especially land-use changes and an intensification of agricultural management caused an unprecedented loss of biodiversity in agroecosystems worldwide. Concerns have been raised that the ongoing loss of biodiversity would ultimately lead to impaired ecological interactions and ecosystem functioning in agricultural landscapes. In order to stop biodiversity loss while producing enough food for a growing world population, we need to gain detailed knowledge on ecological interactions and the functioning of agroecosystems as a whole.
Bats (Chiroptera) represent an important component of global biodiversity, occupy a variety of ecological niches and fulfill numerous ecosystem services. Especially in temperate zone agroecosystems, bats were repeatedly reported to contribute to the reduction of pest insects above intensively managed arable fields. However, bat populations have been decimated by the consequence of land-use intensification which led to their legal protection status in the European Union (Council of Europe, 1979). The increasing number of wind turbines on arable fields poses an additional threat to bats as they might get injured or killed when flying too close to wind turbine blades. Although a large amount of land area is covered by arable fields, not much is known about how bats use the intensively managed agricultural landscape.
In the present thesis, my general aim was to identify the relevance of factors at different spatiotemporal scales for shaping species-specific bat activity above intensively managed arable fields. Therefore, I repeatedly monitored bat activity above open arable fields in a landscape dominated by agriculture which is located in Northeast Brandenburg, Germany. From 2012 to 2014, I recorded echolocation calls of bats on a total of 113 sites using a passive acoustic approach. I obtained a total of 27,779 recordings, identified the recorded echolocation calls manually to species level and calculated species-specific bat activity measures. Depending on the focus of research, I modeled the obtained species-specific activity measures using generalized linear and additive mixed effect models. In Chapter I, I focused on identifying seasonal patterns in several species-specific activity measures of different functional bat groups. In Chapter II, I investigated small-scale effects of landscape elements, such as hedgerows and forest edges, on the flight and foraging activity of different bat species along the edge-field interface. Additionally, I aimed at identifying whether these effects are influenced by small ponds located within arable field and whether these effects change across seasons. In Chapter III, my aim was to investigate the interaction between factors from different spatiotemporal levels on the flight and foraging activity of bats above arable fields. At the small spatial scale, I focused on prey availability, at a large spatial scale on selected parameters which describe landscape characteristics and at the temporal scale on seasonal effects.
The major findings obtained in each chapter can be summarized in the following three points. The first major finding is that not only landscape elements on a small spatial scale, e.g. a hedgerow at the edge of an arable field, but also landscape characteristics on a large spatial scale, e.g. landscape composition, shaped species-specific bat activity above open arable fields. This activity was also strongly influenced by interactions between landscape characteristics and local prey availability. Second, the influence of landscape elements and characteristics on bat activity above arable fields was not constant over time but changed across seasons with the strongest impact during summer as compared to spring and autumn. Third, I found indications of ecosystem service provided by N. noctula and P. nathusii in all three chapters, as especially these bat species were repeatedly found to forage above arable fields. This foraging activity was positively influenced by the proximity to landscape elements at the edge of the arable field but also by the presence of small ponds within the arable field.
In light of the obtained findings, I strongly recommend protecting and most importantly recreating semi-natural landscape elements in the agricultural landscape. Furthermore, I strongly recommend against the construction of wind turbines close to these linear woody vegetation edges as bats were found to be active close to these landscape elements. Additionally, the operation times for wind turbines should be down-regulated during the mating and migration period in autumn due to high bat activity above arable fields. Since bats are considered being good bioindicators, effective conservation measures for bats might contribute to the protection of species from other taxa leading to an overall support of biodiversity in agricultural landscapes. In their entirety, the findings in this thesis contribute to the knowledge of different aspects of bat ecology and shed light on the complex interplay between factors from different spatiotemporal levels that shape bat activity above arable fields. Additionally, they can serve as a basis for the improvement and development of conservation measures for bats in agricultural landscapes.
Background
Non-typhoid Salmonella Typhimurium (S. Typhimurium) accounts for a high number of registered salmonellosis cases, and O-serotyping is one important tool for monitoring epidemiology and spread of the disease. Moreover, variations in glucosylated O-antigens are related to immunogenicity and spread in the host. However, classical autoagglutination tests combined with the analysis of specific genetic markers cannot always reliably register phase variable glucose modifications expressed on Salmonella O-antigens and additional tools to monitor O-antigen glucosylation phenotypes of S. Typhimurium would be desirable.
Results
We developed a test for the phase variable O-antigen glucosylation state of S. Typhimurium using the tailspike proteins (TSP) of Salmonella phages 9NA and P22. We used this ELISA like tailspike adsorption (ELITA) assay to analyze a library of 44 Salmonella strains. ELITA was successful in discriminating strains that carried glucose 1-6 linked to the galactose of O-polysaccharide backbone (serotype O1) from non-glucosylated strains. This was shown by O-antigen compositional analyses of the respective strains with mass spectrometry and capillary electrophoresis. The ELITA test worked rapidly in a microtiter plate format and was highly O-antigen specific. Moreover, TSP as probes could also detect glucosylated strains in flow cytometry and distinguish multiphasic cultures differing in their glucosylation state.
Conclusions
Tailspike proteins contain large binding sites with precisely defined specificities and are therefore promising tools to be included in serotyping procedures as rapid serotyping agents in addition to antibodies. In this study, 9NA and P22TSP as probes could specifically distinguish glucosylation phenotypes of Salmonella on microtiter plate assays and in flow cytometry. This opens the possibility for flow sorting of cell populations for subsequent genetic analyses or for monitoring phase variations during large scale O-antigen preparations necessary for vaccine production.