25 research outputs found
The biogeochemical iron cycle and astrobiology
Biogeochemistry investigates chemical cycles which influence or are influenced by biological activity. Astrobiology studies the origin, evolution and distribution of life in the universe. The biogeochemical Fe cycle has controlled major nutrient cycles such as the C cycle throughout geological time. Iron sulfide minerals may have provided energy and surfaces for the first pioneer organisms on Earth. Banded iron formations document the evolution of oxygenic photosynthesis. To assess the potential habitability of planets other than Earth one looks for water, an energy source and a C source. On Mars, for example, Fe minerals have provided evidence for the past presence of liquid water on its surface and would provide a viable energy source. Here we present Mössbauer spectroscopy investigations of Fe and C cycle interactions in both ancient and modern environments. Experiments to simulate the diagenesis of banded iron formations indicate that the formation of ferrous minerals depends on the amount of biomass buried with ferric precursors rather than on the atmospheric composition at the time of deposition. Mössbauer spectra further reveal the mutual stabilisation of Fe-organic matter complexes against mineral transformation and decay of organic matter into CO2. This corresponds to observation of a ‘rusty carbon sink’ observed in modern sediments. The stabilisation of Fe-organic matter may also aid transport of particulate Fe in the water column while having on adverse effect on the bioavailability of Fe. In the modern oxic ocean, Fe is insoluble and particulate Fe represents an important source. Collecting that particulate Fe yields small sample sizes that would pose a challenge for conventional Mössbauer experiments. We demonstrate that the unique properties of the beam used in synchrotron-based Mössbauer applications can be utilized for studying such samples effectively. Reactive Fe species often occur in amorphous or nanoparticulate form in the environment and are therefore difficult to study with standard mineralogical tools. Sequential extraction techniques are commonly used as proxies. We provide an example where Mössbauer spectroscopy can replace sequential extraction techniques where mineralogical information is sought. Where mineral separation is needed, for example in the investigation of Fe or S isotope fractionation, Mössbauer spectroscopy can help to optimize sequential extraction procedures. This can be employed in large number of investigations of soils and sediments, potentially even for mineral separation to study Fe and S isotope fractionation in samples returned from Mars, which might reveal signatures of biological activity. When looking for the possibility of life outside Earth, Jupiter’s icy moon Europa is one of the most exciting places. It may be just in reach for a Mössbauer spectrometer deployed by a future lander to study the red streak mineral deposits on its surface to look for clues about the composition of the ocean hidden under the moon’s icy surface
The Phosphorus Economy of Mediterranean Oak Saplings Under Global Change
While a severe decrease in phosphorus (P) availability is already taking place in a large number of ecosystems, drought and nitrogen (N) deposition will likely further decrease the availability of P under global change. Plants have developed physiological strategies to cope with decreasing P resources, but it is unclear how these strategies respond to elevated N deposition and summer droughts. We investigated the influence of N and P availability and soil drought on P uptake (H333PO4 feeding experiment) and use efficiencies in young Quercus calliprinos Webb. trees. We hypothesized that (H1) the expected increases in soil N:P ratios will increase the efficiencies of P uptake and use of oak saplings but will decrease the efficiencies of N uptake and use, whereas (H2) drought will affect P uptake efficiency more than N uptake efficiency. In confirmation of (H1) we found that a sharp increase of the soil N:P ratio from 4 to 42 g g-1 significantly increased the instantaneous 33P uptake efficiency (33PUptakeE) by five-fold and long-term P uptake efficiency (PUptakeE) by six-fold, while it decreased N uptake efficiency (NUptakeE) and N use efficiency (NUE). In contradiction to (H1), P use efficiency (PUE) did not respond to the simulated extended gradient of soil N:P ratios but remained relatively constant. (H2) was only partially confirmed as soil drought reduced PUptakeE by up to a fourth at high soil N:P ratios but had no significant effect on NUptakeE. As a consequence, increasing summer droughts may decrease the response of PUptakeE to increasing P limitation, which – in the absence of adjustments of the efficiency of P use – can aggravate growth reductions in this eastern Mediterranean tree species under global change
Reassessing evidence of Moon–Earth dynamics from tidal bundles at 3.2 Ga (Moodies Group, Barberton Greenstone Belt, South Africa)
Past orbital parameters of the Moon are difficult to reconstruct from geological records because relevant data sets of tidal strata are scarce or incomplete. The sole Archean data point is from the Moodies Group (ca 3.22 Ga) of the Barberton Greenstone Belt, South Africa. From the time-series analysis of tidal bundles from a well-exposed subaqueous sand wave of this unit, Eriksson and Simpson (Geology, 28, 831) suggested that the Moon’s anomalistic month at 3.2 Ga was closer to 20 days than the present 27.5 days. This is in apparent accordance with models of orbital mechanics which place the Archean Moon in a closer orbit with a shorter period, resulting in stronger tidal action. Although this study’s detailed geological mapping and section measuring of the site confirmed that the sandstone bed in question is likely a migrating dune, the presence of angular mud clasts, channel-margin slumps, laterally aggrading channel fills and bidirectional paleocurrents in overlying and underlying beds suggests that this bedform was likely located in a nearshore channel near lower-intertidal flats and subtidal estuarine bars; it thus carries risk of incomplete preservation. Repeated measurements of foreset thicknesses along the published traverse, measured perpendicular to bedding, failed to show consistent spectral peaks. Larger data sets acquired along traverses measured parallel to bedding along the 20.5 m wide exposure are affected by minor faulting, uneven outcrop weathering, changing illumination, weather, observer bias and show a low reproducibility. The most robust measurements herein confirm the periodicity peak of approximately 14 in the original data of Eriksson and Simpson (Geology, 28, 831). Because laminae may have been eroded, the measurements may represent a lower bound of about 28 lunar days per synodic month. This estimate agrees well with Earth–Moon dynamic models which consider the conservation of angular momentum and place the Archaean Moon in a lower orbit around a faster-spinning Earth
Reassessing evidence of Moon–Earth dynamics from tidal bundles at 3.2 Ga (Moodies Group, Barberton Greenstone Belt, South Africa)
Past orbital parameters of the Moon are difficult to reconstruct from geological records because relevant data sets of tidal strata are scarce or incomplete. The sole Archean data point is from the Moodies Group (ca 3.22 Ga) of the Barberton Greenstone Belt, South Africa. From the time-series analysis of tidal bundles from a well-exposed subaqueous sand wave of this unit, Eriksson and Simpson (Geology, 28, 831) suggested that the Moon’s anomalistic month at 3.2 Ga was closer to 20 days than the present 27.5 days. This is in apparent accordance with models of orbital mechanics which place the Archean Moon in a closer orbit with a shorter period, resulting in stronger tidal action. Although this study’s detailed geological mapping and section measuring of the site confirmed that the sandstone bed in question is likely a migrating dune, the presence of angular mud clasts, channel-margin slumps, laterally aggrading channel fills and bidirectional paleocurrents in overlying and underlying beds suggests that this bedform was likely located in a nearshore channel near lower-intertidal flats and subtidal estuarine bars; it thus carries risk of incomplete preservation. Repeated measurements of foreset thicknesses along the published traverse, measured perpendicular to bedding, failed to show consistent spectral peaks. Larger data sets acquired along traverses measured parallel to bedding along the 20.5 m wide exposure are affected by minor faulting, uneven outcrop weathering, changing illumination, weather, observer bias and show a low reproducibility. The most robust measurements herein confirm the periodicity peak of approximately 14 in the original data of Eriksson and Simpson (Geology, 28, 831). Because laminae may have been eroded, the measurements may represent a lower bound of about 28 lunar days per synodic month. This estimate agrees well with Earth–Moon dynamic models which consider the conservation of angular momentum and place the Archaean Moon in a lower orbit around a faster-spinning Earth
The genomes of two key bumblebee species with primitive eusocial organization
Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation
Evaluation of ergoline derivatives with antiplasmodial activity and in vitro bioactivity-guided fractionation of tropical medicinal plants traditionally used as antimalarials
0 Titelblatt
1 Einleitung
1.1 Malaria
1.2 Exostema mexicanum GRAY (Rubiaceae)
1.3 Calea tenuifolia KUNTH (Asteraceae)
1.4 Microglossa pyrifolia (LAM.) KUNTZE (Asteraceae)
1.5 Natürliche und semisynthetische Ergolinderivate
1.6 Zielsetzung
2 Hauptteil
2.1 Screening verschiedener Heilpflanzen aus El Salvador
2.2 Screening verschiedener Heilpflanzen aus Ghana
2.3 Exostema mexicanum GRAY
2.4 Calea tenuifolia KUNTH
2.5 Microglossa pyrifolia (LAM.) KUNTZE
2.6 Berechnung des log P-Wertes und log D-Wertes
2.7 Untersuchung weiterer Pflanzenextrakte
2.8 Untersuchung von monomeren Ergolinen und ihren semisynthetischen N,
N'-verknüpften oligomeren Derivaten
3 Diskussion
3.1 Untersuchungen von Exostema mexicanum GRAY (Rubiaceae)
3.2 Untersuchungen von Calea tenuifolia KUNTH (Asteraceae)
3.3 Untersuchungen von Microglossa pyrifolia (LAM.) KUNTZE (Asteraceae)
3.4 Bedeutung von Heilpflanzen in der traditionellen Malariatherapie
3.5 Antiplasmodiale Wirkung von monomeren Ergolinen und ihren
semisynthetischen N, N'-verknüpften oligomeren Derivaten
3.6 Ausblick
4 Zusammenfassung
5 Experimenteller Teil
5.1 Pflanzenmaterial
5.2 In-vitro-Testsystem gegen Plasmodium falciparum
5.3 Untersuchung zur Zytotoxizität
5.4 Log P- und log D-Wert-Berechnung
5.5 Phytochemische Methoden
5.6 Isolierung der Verbindungen aus aktiven Fraktionen von Exostema mexicanum
5.7 Eigenschaften der isolierten Verbindungen aus den Zweigen und der
Stammrinde von Exostema mexicanum
5.8 Isolierung der Verbindungen aus aktiven Fraktionen von Calea tenuifolia
5.9 Eigenschaften der isolierten Verbindungen aus den Blättern von Calea
tenuifolia
5.10 Isolierung der Verbindungen aus aktiven Fraktionen von Microglossa
pyrifolia
5.11 Eigenschaften der isolierten Verbindungen aus M. pyrifolia
5.12 Synthese von 19-Hydroxy-6E,10E,14E-geranylgeraniol (32)
5.13 Untersuchung weiterer Pflanzendrogenextrakte
5.14 Synthese der semisynthetischen N,N'-verknüpften Ergolinoligomere
6 Abkürzungsverzeichnis
7 Literatur
8 AnhängeEs wurden zentralamerikanische und westafrikanische Heilpflanzen untersucht,
deren Anwendung in der traditionellen Malariatherapie aufgrund von
Literaturdaten bzw. ethnobotanischen Informationen bekannt war. Von acht
Pflanzenarten El Salvadors und elf pflanzlichen Drogen Ghanas, die jeweils in
der landeseigenen traditionellen Phytotherapie angewendet werden, wurden aus
verschiedenen Pflanzenteilen Rohextrakte unterschiedlicher Polaritaet
hergestellt. Diese Extrakte wurden einem in-vitro-Testsystem zugefuehrt um
deren Hemmwirkung gegenueber dem Chloroquin-sensiblen Stamm PoW und dem
Chloroquin-resistenten Klon Dd2 von Plasmodium falciparum zu bestimmen.
Aufgrund der gezeigten antiplasmodialen Aktivitaet wurden die Rindendroge von
Exostema mexicanum GRAY (Rubiaceae), die Blattdroge von Calea tenuifolia KUNTH
(Asteraceae) und die oberirdischen Pflanzenteile von Microglossa pyrifolia
(LAM.) KUNTZE (Asteraceae) im Sinne einer aktivitaetsgeleiteten Fraktionierung
untersucht. Aus aktiven Fraktionen von E. mexicanum wurden sieben
4-Phenylcumarine erhalten. Bei 4',5,7,8-Tetramethoxy-4-phenylcumarin [O
-Methyl-exostemin], 4',8-Dihydroxy-5,7-dimethoxy-4-phenylcumarin [Exomexin A]
und 3',4'-Dihydroxy-5,7,8-trimethoxy-4-phenylcumarin [Exomexin B] handelt es
sich um neue Naturstoffe. Die hoechste antiparasitaere Hemmwirkung besass O
-Methyl-exostemin (IC50-Werte: 10,5 µM [PoW] und 4,7 µM [Dd2]). Zusaetzlich
wurde von allen aktiven Verbindungen der zytotoxische Effekt an der humanen
Endothelzelllinie ECV 304 untersucht. Hierbei zeigten die getesteten
4-Phenylcumarine eine signifikante zytotoxische Aktivitaet mit IC50-Werten
zwischen 1,2 µM und 10,0 µM. Alle erhaltenen in-vitro-Daten deuten daraufhin,
dass eine uneingeschraenkte phytotherapeutische Anwendung von E. mexicanum
nicht empfohlen werden kann. Aus aktiven Fraktionen von C. tenuifolia konnten
fuenf Flavone und zwei ungesaettigte Fettsaeuren isoliert werden, die alle
eine antiplasmodiale in-vitro-Aktivitaet aufwiesen. Die hoechste Hemmwirkung
gegenueber dem Parasiten zeigte 7-Methylacacetin (IC50-Werte: 20,1 µM [PoW]
und 17,1 µM [Dd2]). Alle Inhaltsstoffe wurden dem in-vitro-Zytotoxizitaetstest
an der humanen Endothelzelllinie ECV 304 zugefuehrt. Anhand der erhaltenen in-
vitro-Daten kann die phytotherapeutische Relevanz von C. tenuifolia nicht
vollstaendig bewertet werden. Jedoch konnte die antiplasmodiale Aktivitaet der
zentralamerikanischen Heilpflanze in vitro bestaetigt werden. Die
aktivitaetsgeleitete Fraktionierung von M. pyrifolia fuehrte zur Isolierung
von achtzehn Inhaltsstoffen, u.a. verschiedene Furanoditerpene und
Geranylgeraniol-Derivate. Bei Sinapyldiangelat und 1-Acetyl-6E,10E,14E-
geranylgeraniol-19-carbonsaeure und 19-Oxo-6E,10E,14E-geranylgeraniol handelt
es sich um neue Naturstoffe. Die hoechste Hemmwirkung gegenueber P. falciparum
wiesen 2E-Phytol und 6E,10E,14E-Geranylgeraniol-19-carbonsaeure auf
(IC50-Werte zwischen 8,4 µM [PoW] und 16,3 µM [Dd2]). Die aktiven Verbindungen
besassen eine geringe Zytotoxizitaet gegenueber ECV 304 mit IC50-Werten
zwischen 95,6 µM und 200,2 µM bzw. erwiesen sich als nicht zytotoxisch. Im
Laufe der Untersuchungen an M. pyrifolia konnte die antiplasmodiale in-vitro-
Aktivitaet der Droge nachgewiesen werden. In einer weiteren Studie wurde die
antiparasitaere in-vitro-Wirkung von monomeren Ergolinen und semi-
synthetischen N,N'-verknuepften Oligomeren, mit Festuclavin, Tergurid und
Pergolid als Monomer, bestimmt. Die Ergebnisse zeigten, dass eine N?1,N?1'-
bzw. eine N-6,N-6'-Dimerisierung zu einer Erhoehung der antiplasmodialen
Aktivitaet fuehrte. Fuer ein N-6,N-6'-verknuepftes Dimer mit Depropylpergolid
als Monomer wurde die staerkste Hemmwirkung festgestellt (IC50-Werte: 0,14 µM
[PoW] und 0,13 µM [Dd2]). Von allen Verbindungen wurde zusaetzlich der
zytotoxische Effekt an der murinen Fibroblastenzelllinie NIH 3T3 bestimmt.
Fuer weitergehende Untersuchungen sind ein N-1,N-1'-verknuepftes Tergurid-
Tetramer und ein N-1,N-1'-substituiertes Festuclavin-Trimer von Interesse.
Beide Verbindungen erwiesen sich als nicht zytotoxisch bei einer gleichzeitig
guten antiplasmodialen Wirkung mit IC50-Werten zwischen 0,54 µM [Dd2] und 1,53
µM [Dd2].Malaria is still the most dangerous parasitic infectious disease causing
millions of deaths every year. In many countries where Malaria is endemic the
traditional medical methods constitute a strong part in the public health care
system. Phytochemical research on medicinal plants traditionally used as
antimalarials are urgently needed. In this context we looked at several
Central American and West African medicinal plants, which are traditionally
used against malaria and/or symptoms of the disease. Analysis of all plant
species was based on literature and/or ethnobotanical studies. We produced
plant extracts of different polarity from various plant parts of eight species
from El Slavador and eleven species from Ghana, which are still used in the
Central American and West African traditional phytotherapy, All extracts were
tested for their in vitro actvity against a Chloroquine-sensitive strain PoW
and a Chloroquine-resistent clone Dd2 of Plasmodium falciparum. The stem bark
from Exostema mexicanum Gray (Rubiaceae), the leaves from Calea tenuifolia
Kunth (Asteraceae), and the aerial parts from Microglossa pyrifolia (Lam.)
Kuntze (Asteraceae) exhibited a promising antiplasmodial activity. Thus
bioactivity-guided fractionations were carried out in order to isolate and
characterize the major antiprotozoan principles of this species. Further
purification of the active lipophilic extract (petrol ether/ methanol 1:1) and
the methanolic extract of E. mexicanum led to the isolation of seven
4-phenylcoumarines, with 4',5,7,8-tetramethoxy-4-phenylcoumarin [O-methyl-
exostemin], 4',8-dihydroxy-5,7-dimethoxy-4-phenylcoumarin [exomexin A], and
3',4'-dihydroxy-5,7,8-trimethoxy-4-phenylcoumarin [exomexin B] as new natural
compounds. O-Methyl-exostemin showed a significant activity against P.
falciparum (IC50-values: 10.5 µM [PoW] and 4.7 µM [Dd2]). Additionally, of all
active compounds the cytotoxic effect on the human endothelium cell line (ECV
304) in vitro were assessed. Here, all tested 4-phenylcoumarines exhibited a
significant cytotoxic activity with IC50-values between 1,2 µM and 10,0 µM.
Given this result, the unrestricted use of the E. mexicanum as an
ethnomedicinal substance cannot be recommended based. Bioactivity-guided
fractionation of the lipophilic leaf extract of C. tenuifolia led to the
isolation of five flavones and two unsaturated fatty acids. All compounds
showed activities against P. falciparum, with 7-methylacacetin exhibiting the
strongest inhibition of the parasite (IC50-values: 20.1 µM [PoW] and 17.1 µM
[Dd2]). All seven compounds were also tested on the human endothelium cell
line (ECV 304). Based on our results, we cannot completely assess the
antiplasmodial potential of this plant species. However our findings may
represent a rational explanation for a potential antimalarial effect of the
leaves of C. tenuifolia. Bioactivity-guided fractionation of the aerial parts
of M. pyrifolia lead to the isolation of 18 natural compounds, e.g. different
furanoditerpenes and geranylgeraniol derivatives. Sinapyl diangelate, 1
-acetyl-6E, 10E, 14E-geranylgeraniol-19-oic acid and 19-oxo-6E, 10E, 14E-
geranylgeraniol were identified as new natural compounds. The strongest
inhibition of P. falciparum could be observed for 2E- phytol and 6E, 10E, 14E-
geranylgeraniol-19-oic acid with IC50-values ranging from 8.4 µM [PoW] to 16.3
µM [Dd2]. All active compounds showed only a weak cytotoxic effect on ECV 304
with IC50-values between 95.6 µM and 200.2 µM, or they were not cytotoxic.
From several active fractions we isolated 6E, 10E, 14E-geranylgeraniol-19-oic
acid. This diterpene was also detectable in the aqueous extract despite of its
rather lipophilic character. Therefore, we assume that the aliphatic
unsaturated compounds are representing the antiprotozoan principle of this
species, and 6E, 10E, 14E -geranylgeraniol-19-oic acid supposed to be mainly
responsible for a moderate antiplasmodial activity of a traditional plant
preparation of M. pyrifolia. During another study, the three monomeric
ergolines terguride, festuclavine, pergolide, and their N, N'-spacer-linked
oligomeric derivatives have been investigated for their in vitro activity
against P. falciparum. All monomers have shown only a weak antiplasmodial
effect, but either N-1, N-1'- or N-6, N-6'-spacer-linked dimerization are able
to enhance their antiparasitic activity. A N-6, N-6?-spacer-linked
depropylpergolide dimer exhibited the highest activities with IC50-values of
0.14 µM and 0.13 µM against PoW and Dd2, respectively. Additionally from all
tested compounds the cytotoxic effects against mouse fibroblasts (NIH 3T3) in
vitro were evaluated. For further studies a N-1, N-1'-spacer-linked
festuclavine trimer and a N-1, N-1'-spacer-linked terguride tetramer are
interesting. Both compounds were not cytotoxic and possessed good
aniplasmodial activities with IC50-values between 0.54 µM and 1.53 µM against
Dd2